Achieving Intelligibility whilst Maintaining Heaviness when Producing Contemporary Metal Music

1. Introduction

Metal is part of the Westernised, commercial pop and rock music industry that has imposed itself on the rest of the world… metal has played and continues to play a key role in the globalised entertainment industries.  (Hill and Spracklen, 2010, p.vii)

The term ‘heavy metal’ was first used as an adjective relating to popular music in the late 1960s, however in the early 1970s the expression began to be employed as a noun and therefore as a descriptor for a music genre (Walser, 1993, p.7). Heavy metal has therefore existed for approximately four decades. In the past five years there has been a dramatic increase in academics researching and studying the area (Scott and Von Helden, 2010, p.ix). This is evidenced by the world’s first scholarly conference on the metal genre, ‘Heavy Fundametalisms – Music, Metal and Politics’, being held in Salzburg, Austria in 2008 (Sheppard, 2008). To date, the focus of this academic study has tended to address the importance and relevance of metal from a historical, sociological, cultural, musicological and political science perspective (e.g. Weinstein, 1991; Walser, 1993; McIver, 2000, 2002, 2005; Kahn-Harris, 2007) and additionally, Weinstein points to metal studies comprehending the fields of economics, literature, communications and social psychology (Weinstein, 2011, p.243). In contrast, this paper focuses on the specific approaches and techniques involved in music production for this style and builds on the author’s previous work in the area.

2. Fragmentation

Following the emergence of heavy metal music in the early 1970s, the 1980s witnessed it’s ascent in popularity and success. This continued throughout the decade with heavy metal becoming one of America’s foremost forms of popular music, for example (Walser, 1993, p.3); however, this period was also marked by the process of heavy metals fragmentation, which reached its culmination in the 1990s (Kahn-Harris, 2007, p.2). This fragmentation took the form of the music evolving, dividing and multiplying into numerous subgenres. These subgenres include, but are not restricted to: speed/thrash metal, doom metal, death metal, rap metal, neo-classical metal, nu-metal, black metal, hardcore metal, grindcore, industrial metal, progressive metal, post-metal, gothic metal and symphonic metal. The differences between these subgenres, although sometimes subtle, tend to revolve around song tempi, drumming technique, overall instrumentation, song structure, level and manner of guitar and bass down-tunings, rhythm and lead guitar playing techniques, lyrical content and vocal approach (Moynihan and Søderlind, 1998; Purcell, 2003; Mudrian, 2004; Kahn-Harris, 2007).

However, attempting to set out the musical parameters of metal music is highly problematic (Shuker, 2005, p.132), as metal embraces a wide range of musical influences (Walser, 1993, pp.3-4). Similarly, any attempt to provide a specific scheme of classification for any of metal music’s multiple subgenres also presents numerous challenges (Berger, 1999b, p.56; Azevedo, 2010, p.322). Therefore, to avoid any possible debate about the accuracy of their application, this paper will avoid the use of specific subgenre designators. Additionally, the broader term heavy metal will be avoided. This is for the reason that, in recent years, this term has been adopted as a way of describing bands that perform a mode of metal music whose performance and artistic approach is similar to that heard before metal music evolved and hybridised into these numerous subgenres.

3. Contemporary Metal

The collective, generic term contemporary metal (CM) will be used. CM is a term sometimes used by metal studies academics (e.g. Rafalovich and Schneider, 2005; Rafalovich, 2006; Brown, 2007, 2011) and the metal music media to collectively differentiate bands demonstrating qualities associated with metal music’s subgenres, rather than those qualities employed for traditional heavy metal. Roy Shuker (2005) uses the term contemporary heavy metal in his ‘Popular Music: The Key Concepts’ publication, which presents a glossary of the main terms and concepts used in the study of popular music. Referring to the multiple subgenres that resulted from metal music’s fragmentation and hybridisation, and equating CM with these, Shuker proposes:

There are a number of identifiable heavy metal subgenres, or closely related styles. Although these are historically specific, each has continued to be represented in the complex range of contemporary heavy metal. (Shuker, 2005, p.133)

4. Defining Attributes of CM Production

CM artists will often explore different dynamics, styles and expressions within one song (Hoffstaft and Nagenborg, 2010, p.41). Despite this, the defining features of a high commercial standard of production are firstly heaviness and sonic weight, and secondly a high level of definition and intelligibility of the instrumentation involved, which is fundamental to retaining, and providing, sonic clarity for the often-complex performances and advanced standards of musicianship.  These characteristics could be considered as being part of the style’s unspoken aesthetic code.

5. Performance Attributes

For CM, the standard of drum performances are frequently, but not always, technically complex, virtuoso performances, which are often marked by an intricacy and aggression of the beats, patterns and subdivisions employed, and the speed and stamina of the double bass drum work involved. These complex double bass drum subdivisions have a tendency to accentuate, syncopate or synchronise with the rhythm patterns of the guitar performances (Turner, 2009, p.6), which have an inclination to revolve more around rhythm than melody. This is highly effective in providing CM’s sense of intensity, density, and heaviness. However these qualities present numerous challenges to retaining definition and intelligibility, which is fundamental to presenting a high level of sonic clarity for these often-complex performances.

6. Down Tuning and Heaviness

Heaviness is the defining feature of the genre. (Berger and Fales, 2005, p.181)

In addition to a distinct intensification of the energy levels, aggression, complexity, intensity and general standard of performance displayed when compared to traditional modes of metal, there has additionally been a marked increase in the heaviness of bass and guitar tones involved with CM. This is normally facilitated by the now widespread use of down tuning, also known as dropped tuning, which is a term used to describe a musical instrument deliberately tuned with a lowered system of pitches. Pitch can be seen as vital to the overall sonic impact of metal, and down tuning provides a deeper, heavier and darker tonality. Furthermore, a greater movement of air is created from loudspeakers reproducing these amplified tones, due to the lower fundamental frequency. Due to the fundamental of a down tuned bass residing below the range of most domestic hi-fi systems, and the rhythm guitars occupying the range normally occupied by the bass drum and bass guitar, this causes several challenges to achieving a heavy, yet tight and controlled low end, that retains bass and rhythm guitar note definition and clarity.

Additionally, CM guitar tones have been impacted by the development of high gain valve amplification technology, which are better suited to the lower pitch of the tonalities involved. This provides the ability for musicians and producers to achieve significantly heavier and denser rhythm guitar tones. Additionally, in striving for a heavy, dense sound, CM rhythm guitar tones have a tendency to be ‘quad-tracked’, which in this instance, refers to CM’s rhythm guitar sound often consisting of four separate performances. In context of the overall production, these highly distorted, down tuned and dense guitar tones provide numerous challenges to gaining the appropriate weight, as well as clarity and intelligibility, of the drums and bass guitar.

7. Heaviness

7.1 Frequency Content

Although the term can be used to refer to a wide range of instrumental timbres (Berger and Fales, 2005, p.187), for popular music purposes, the term ‘heavy’ is most frequently associated with the metal genre (Reyes, 2008, p.3). The adjective is mainly used to depict the sonic weight and density of the low and low-mid frequencies displayed by acts from this style. Appropriately controlling and sculpting these low-end frequencies is the principal challenge when producing the genre (Sneap, 2009) and it can be noted that the lowered pitches involved with the use of down tuning provides an extended low frequency content when compared to standard A440 tuning.

However, to restrict the focus of the concept of ‘heaviness’ to the low and low-mid frequency ranges alone would be a mistake. The upper mid range, as well as treble and presence range, are essential for achieving a thick, sharp and aggressive overall tonality from much of the instrumentation involved, and this tonality can contribute considerably to the perception of heaviness. This premise particularly applies to distorted guitar timbres, which are most commonly associated with the concept of ‘heaviness’ (Walser, 1993, p.2; Berger, 1999b, p.58). One of the results of Berger and Fales’ study demonstrated that guitar timbres are perceived as heavier when more high frequency energy is introduced (Berger and Fales, 2005, pp.193-194). However, Zagorski-Thomas’ review of this text highlighted that changes in mastering technology and techniques could also account for these changes (Zagorski-Thomas, 2007, p.695).

Similar to the introduction of more high frequency energy with more modern guitar sounds, CM bass drum sounds also have a tendency towards containing a lot more high frequency content than displayed in traditional metal. This is particularly so when compared to most other styles of rock music with similar instrumentation. This high frequency content for the genre’s bass drums is often referred to as ‘clickiness’ and of all the drum kit’s constituent parts, the bass drums on productions from the genre will normally bear the least resemblance to the natural acoustic properties of the source.

Clearly, bass guitar tonalities have a considerable bearing on a productions’ sense of heaviness, and these can be viewed as being heavy when their impact gives the sense of having weight, size and depth. However, one of the challenges created by dense layers of down tuned distorted guitars is getting the rhythm guitar and bass to sit together ‘frequency-content’ wise. Rhythm guitars are generally considered as needing to occupy the mid-range, however here, the down tuned guitars have a fundamental frequency that is occupying the area normally allocated to the bass drum and bass guitar. Therefore, it can often be the case that bass sounds which ordinarily, in isolation, embody the qualities of weight, size and depth will not work within the context of the rhythm guitars, and therefore the mix overall. Additionally, the fundamental frequencies of down tuned bass guitars are not usually recreated efficiently by most domestic playback systems. This is due to the loudspeaker excursion required to generate this region of frequencies being beyond the frequency range capabilities of the majority of mass produced consumer loudspeakers.

7.2 Frequency Content and Masking

From a mix perspective, in striving for a ‘heavy’ result, many producers will excessively amplify incorrect low-end frequencies, resulting in an uncontrolled, boomy and flabby mix. Alternatively, a mix with a deficiency of the correct bass frequencies will sound thin and lack impact. The foundation to getting the heaviness of a CM mix right is by creating a very specific place and space for each sound source to sit and breathe. This will partly be achieved by avoiding frequency masking, which is an important sonic phenomena when mixing CM. In simple terms, masking is the ability of frequencies of one sound to obscure, or inhibit, (i.e. mask) the frequencies of another sound. From a mixing perspective, this equates to combining two or more instruments containing similar frequencies. These effectively fight for the same sonic space, with the quieter or weaker of these sounds having this range of frequencies obscured or made inaudible by the louder or more dominant one (Izhaki, 2007). Avoiding masking in a mix is a fundamental aspect of heaviness and perceived loudness, due to the fact that this phenomenon especially occurs in a dense mix, and is more pronounced in low frequencies. As stated, avoiding masking can be achieved by creating a very specific place and space for each sound source to sit and breathe.

7.3 Density of Sounds

In addition to capturing and presenting the most appropriate frequency content for the instrumentation involved, the density of these sounds, particularly the bass drum, bass and rhythm guitar, is an essential contributing factor in providing a production that is perceived as being sonically ‘heavy’. The principal consideration concerning frequency content and density of sounds is ensuring that the most appropriate sound is captured at source. This will involve the most suitable equipment being used, the tuning of the drums, microphone placement etc. etc.

However, other than these considerations, the foremost production technique for providing density is by means of the layering of sounds, which will strengthen the coverage of frequencies. In the instance of the bass drums, the use of sample reinforcement/augmentation, or replacement, is often employed. Here, an appropriate bass drum sample, which will have been created from a very hard strike to a bass drum, with no bleed, and already equalised, or alternatively already consisting of layers of these bass drum hits mixed together, will normally be used, and at a fixed dynamic range. In the instance of bass guitar, alternative tones are frequently used to supplement the regular combination of DI (direct injection) combined with microphone. This could, for example, involve the use of amplifier/cabinet/microphone software or hardware emulation, or/and the introduction of a heavily distorted bass signal.

In addition to down tuning, the concept of quad tracking is frequently employed to achieve a dense, heavy rhythm guitar sound. Quad tracking, in this instance, refers to the genre’s rhythm guitar sound often consisting of four separate performances. In the instance of a band line-up consisting of one guitarist, this would usually involve this member recording the exact same rhythm guitar performance on four separate occasions. In the instance of a two-guitar band line-up, this would usually involve each guitarist recording his or her own exact same rhythm guitar parts on two separate occasions. When performed accurately, this technique results in a thicker, and sonically heavier guitar sound. Whilst layering rhythm guitars in this manner, it is beneficial to vary the tones between these four performances by changing an element, or elements, of the guitar equipment, microphone(s) or microphone placement(s) used. This will normally provide enhanced frequency coverage and an even stronger, denser and heavier guitar tone than would be the case with four rhythm performances using the same sound. Two of these rhythm performances will usually be panned hard left, or perhaps with one of these parts not quite hard left, and two panned hard right, or perhaps with one of these parts not quite hard right. Although it would be hard to argue that stereo placement contributes to a metal production’s heaviness, or weight, panning the rhythm guitars very wide in this manner can provide a contribution to the perceived width, and therefore size, of the production.

7.4 Perceived Volume Levels, and Perceived Consistency of Volume Levels

A further essential factor contributing to the concept of ‘heaviness’ and sonic power that signifies the aesthetics of metal music is the perception of high volume levels (Weinstein, 1991, p.23; Walser, 1993, pp.43-45). In addition to the performance characteristics and choice of sounds the musicians in question use, this perception of volume is primarily conveyed through the heavy minimisation of the dynamic range of various elements of the instrumentation, as well as through the use of distortion.

The overall dynamic range of many modern popular music productions has become very small from a macro perspective (Katz, 2002). In this instance macro, or macromixing, refers to the finished mix taken as a whole, whereas micromixing refers to the individual instruments and audio sources that the mix comprises (Izhaki, 2007, p.54). CM productions tend, additionally, to have a very low dynamic range from a micromixing perspective. This is particularly so with the bass drum, bass and rhythm guitars, and this low dynamic range is important for providing the perception of loudness, and therefore heaviness, required of the genre.

In the instance of bass drums, the use of sample reinforcement or replacement, most often implemented at a fixed dynamic level, provides an effective solution to restricting dynamic variation. As Gibson states, compression techniques can be used to provide more volume stability and make sounds more present (Gibson, 2005, p.79). However, the uses of aggressive compression techniques will often not only provide effective restriction of dynamic range, but also present the advantage of increased harmonic content being created of the audio source in question. Due to that more overtones are normally produced when an instrument, in this instance a drum, is struck harder than when it is struck less hard, an increase in overtones will usually be perceived, and associated, with high volume levels. With the bass guitar, aggressive compression to heavily minimise dynamic range is frequently applied in the form of series compression. Furthermore, the introduction of an element of distortion to the bass sound can have the impact of effectively compressing the overall sound.

For rhythm guitars, the impact of distortion:

…simulates the conversion of the guitar from an impulsive to a sustained or driven instrument, and this transformation may be part of the acoustic correlate to the perceptual experience of heaviness.  (Berger and Fales, 2005, p.194).

In effect, distortion provides the rhythm guitar with a flatter dynamic envelope (Berger & Fales, 2005, p.194) and with it an almost infinite sustain, providing a great capacity for sonic power and expression (Walser, 1993, pp.42-43). It is normally the case therefore that rhythm guitars for the metal genre will not need their dynamic range limiting, as, by their nature, they are already compressed.

7.5 Spatial and Depth Characteristics

From a spatial perspective, relating to the perceived depth of CM productions, most of the sounds are very up front, present and close to the listener. Here, the principal reason for sounds being placed up front and close to the listener, as Gibson argues, is that with an increase in distance, sounds are perceived as softer and less intense (Gibson, 2005, p.23). Clearly a decrease in intensity, with sounds being perceived as softer, contradicts the core textural aesthetics of the CM genre.

To place sounds very up front and close to the listener, the genre’s production tends to make minimal use of the natural ambience and room colouration of the recording space. When world-renowned specialist metal producer Colin Richardson (who includes many of the world’s foremost metal acts amongst his extensive credits) was asked about his use of room/ambient microphones, he replied “We don’t use them. The further away you go, the less in your face it sounds. I’ve tried room mics, but I just get into awful trouble with them” (Richardson, 2011). Huber and Runstein note that excluding the acoustic environment creates and tight and present impact (Huber and Runstein, 2005, p.138) and due to the exaggerated sense of aural intimacy that this provides (Zagorski-Thomas, 2008, p.204), close microphone placement, sometimes referred to as spot miking, tends to be standard for CM production.

Worthy of mention, however, is that quad-tracked guitars, which feature four separate performances, sometimes present a slightly ambient quality due to the natural flam that occurs between these layers (Richardson, 2011).

Similarly, restricted use of reverb, which Izhaki refers to as the primary tool for positioning sounds within the depth field (Izhaki, 2007, p.405), is characteristic of the mix stage for CM. Here it is often the case that no more than two different reverbs be used for a mix. Perhaps with one small, tight plate reverb for the snare and toms, and one slightly longer reverb used for the vocals and perhaps clean and solo guitars. In both instances it would be unlikely that longer reverb times, for instance over 1.3 seconds, be used, other than in the event of special effects.

In summation, the spatial and depth characteristics of a CM production can be described as relatively ‘dry’ when compared to other genres of rock music with similar instrumentation.

7.6 Transient Design

In this instance, the term transient design refers to controlling the way a sound begins, continues, then fades, and the variations that it displays over this time. Concepts such as attack and decay, as well as sustain, are frequently applied to describe these variations (Huber and Runstein, 2005, pp.56-57).

Due to the deep and dense sonic characteristics of the bass and rhythm guitar tones, achieving a drum sound that punches through the sonic wall created by these timbres is challenging. The presence of these drum hits provide a fundamental contribution to perceived heaviness. As Moylan points out “important characteristics need to be deliberately shaped or captured to precisely determine the aspect of the recordings aesthetic” (Moylan, 2007, p.264). This is particularly so with the bass drums, which can be considered the most important constituent part of the drums for CM, and are essential for supplying the production with a sense of solidity, drive and urgency.

A bass drum is naturally assumed to have a more consistent tonality than the rest of the shells, due to a bass drum’s beater being at a set, unchanging position. However, the force of the bass drum’s attack during performance is variable. Despite this, retaining or creating consistency to the bass drum’s transient attack is essential for this style. Therefore, the initial stages of transient design for the genre’s bass drums will normally feature the use of drum samples, implemented without any dynamic variation, and Dunkley and Houghton even go as far to say that the use of drum samples is the only way to get the drums to punch through the sonic wall of guitars (Dunkley and Houghton, 2011). Here, an effective bass drum sample will usually have: a hard, clear attack transient; deep and dense, but controlled, low frequencies; sharp and aggressive high frequencies, and will often feature a quite extreme attenuation of the low-mid frequencies. Although it is usual for snare drum sounds for the genre to be relatively dense in order to cut through the rhythm guitars, production for the style will demonstrate large variations in tone. Once again however, retaining and creating consistency of the snare drum’s transient attack is advantageous, and sample reinforcement, or even replacement will achieve this. If the right choices with bass drum or snare drum sample selection are made, then the requirement of further processing, normally in the form of compression or equalisation, may be minimal. However, in many cases, and often when there is less reliance on the use of drum samples, transient design of the bass drum, snare and toms will be required. In the instance of the bass drum, snare and toms, it is often the case that short compression attack times will be avoided. This is to allow the transient attack of the drum hits to be emphasised, in order to punch through the bass and guitar tones.

Sculpting the transient of the bass guitar is similarly important. Although it is important that the note definition of the bass, which is impacted heavily by the transient attack, is retained, it should interact in an appropriate manner with the bass drum, and suitably reinforce and ‘sit’ with the rhythm guitar. Here, the approach to transient design, most often through compression, will be heavily impacted by whether the bassist performed with a plectrum or fingers, the speed and complexity of the performance, as well as the context of the other elements of the production in which the bass will be placed.

The use of distortion on rhythm guitar tones for the CM genre will have normally converted the instrument from being relatively impulsive in nature, to having a relatively small dynamic range (Berger and Fales, 2005, p.194). For this reason, it is usually the case that rhythm guitar tones will not need any transient design.

7.6 Vocal Characteristics

The term ‘heavy’ is most frequently associated with characteristics relating to drums, bass and guitar, as well as the balance of these elements when combined in the context of the overall mix. However, the subjective perception of heaviness can also be impacted by vocal timbre (Berger and Fales, 2005, p.181). Connections between the genre’s heaviness, and the level to which the band or sub-genre avoids melody have been highlighted by some academics (Kahn-Harris, 2007, p.32). This could be said to particularly relate when applied to vocal styles and sounds and their contribution to perceived heaviness. Primarily though, vocals shunning melody would additionally need to be combined with a high level of vocal aggression in order to contribute to a production’s sense of heaviness. Aggressive vocal techniques for the genre are often associated with shouting, thereby resulting in vocal distortion, which, to some degree, can be embellished or simulated with processing during the mix stage. However, it is more likely that a high level of aggression applied at the performance stage would contribute to a production’s sense of heaviness, rather than processing to emulate this. Furthermore, vocals for the genre are likely to exhibit a very small dynamic range, normally achieved through radical compression settings, often applied in series.

7.7 Performance Attributes

The subjective quality ‘heaviness’ can also refer to performance attributes.

8. Definition and Intelligibility

As mentioned, CM’s production values seek to emphasise the definition and intelligibility of the instrumentation involved. As world renowned and highly prolific metal producer Colin Richardson states, due to the methodical and clinical nature of the metal genre’s performances, this clarity is essential to the style (Richardson, 2011).

Definition and intelligibility are often considered to be similar in meaning, but can be distinguished from each other. The term ‘definition’ refers to what it is about a single sound that makes it easy to perceive and understand. In other words, what are the characteristics that a sound source contains that will allow it to be distinct and decipherable? Whilst definition contributes to intelligibility, intelligibility refers to the ease of perception and understanding of a particular instrument or sound source within the context of the mix as a whole. As Izhaki states “Intelligibility is the most elementary requirement of sonic quality” (Izhaki, 2008, p.5) and this statement has particular relevance to CM. Here, it is essential that the intelligibility of the often precise, intense performances, for example fast double-kick drum patterns, be retained.

8.1 Specific Challenges to Definition and Intelligibility

Heaviness is largely associated with the metal genre’s rhythm guitar tones. However these dense, down tuned, heavily distorted, and often quad-tracked, rhythm tonalities present a fundamental and particular challenge to intelligibility. This is principally due to the considerable range of the frequency spectrum that these guitars occupy with increased higher harmonics, combined with potentially endless sustain due to acute harmonic distortion. Although the heaviness, weight and density of these tones embody the essential aesthetic of metal, it is crucial that the low frequencies of the rhythm guitar sound are tight and controlled to retain note definition. Furthermore, it is important that there is a strong level of energy in the high frequencies, the perception of which is vital for an increased sense of heaviness and presence (Berger and Fales, 2005, pp.193-194). These elements are fundamental to achieving a high commercial standard of CM production. However, once these qualities are appropriately presented, this has considerable implications on the techniques required to provide intelligibility to the productions other instrumentation – particularly the bass drum, bass and vocals. For example, gaining vocal intelligibility can be challenging due to that the essential high frequency content of each tends to reside within a similar range. Additionally, this range will normally have been significantly emphasised on the rhythm guitar.

Similarly, the speed of subdivisions frequently employed in CM, for example, double bass drum performances, and fast alternate picking, can be an obstacle to capturing and presenting an appropriate level of definition and intelligibility.

8.2 Presence

Boosting certain frequencies will accentuate the presence of a sound more than others, making it seem even more in your face. (Gibson, 2005, p.23)

Here, Gibson’s statement regarding the accentuation of the presence of sounds making them more ‘in your face’, very much relates to the overall aesthetic requirements of CM. The presence range of frequencies is generally considered to be between 4kHz and 6kHz and this area can be seen as having particularly high relevance to the definition and intelligibility of CM production. This is for the reason that the amplification of this range will normally make the bass drum, snare, bass guitar, rhythm and lead guitar, as well as vocals seem ‘harder’, more distinct and closer. Additionally, Zagorski-Thomas suggests that the amplification of high frequency content suggests intimacy and proximity (Zagorski-Thomas, 2008, p.204). Emphasising these frequencies, therefore, is a principal approach for providing clarity and definition for the instrumentation involved, thereby presenting a clear and coherent production. Furthermore, increasing high, as well as low, frequencies will often result in sounds being perceived as louder than they actually are. This is for the reason that human hearing is more sensitive to low and high frequencies the louder they are in volume (Senior 2011, p.62). Conversely, attenuating the 4kHz to 6kHz presence range of frequencies can result in the relevant sound being perceived as thinner, more distant and softer; and it can be noted that over-amplification of this range of frequencies can cause the audio content in question to sound harsh and abrasive.

However, to restrict the focus of this presence band of frequencies solely to the amplification of this range would be a mistake. As Izhaki points out, equalisation can be looked at from a yin and yang point of view, therefore the greater the level of low frequencies, the less that the higher frequencies will be perceived (Izhaki, 2007, pp.234-236), a perspective that is also highlighted by Maserati (2009). Therefore to increase the apparent level of the 4kHz to 6kHz frequencies of an audio source, a reduction in low-mid frequencies, for example the 300Hz to 500Hz range, could be implemented. Furthermore, there are supplementary benefits to attenuating rather than amplifying frequencies. This is due to the propensity of equalisation to place frequencies out of phase with each other (Izhaki, 2008) and “The more gain there is the more severe the phase artefacts become” (Izhaki, 2008, p.236).

Additionally, it is inadvisable to simultaneously amplify the same range of frequencies on multiple instruments, as this tends to sound unnatural and unpleasant, causing an unpredictable overall mix level, due to the resulting ‘loud’ section created in the frequency spectrum. Furthermore, in many instances, an audio source’s range of frequencies that may require amplification to provide definition and intelligibility may not be within the 4kHz to 6kHz presence range. An example of which would be the bass guitar, where generally speaking, the attack and note definition can be emphasised by amplifying the 2kHz to 3.5kHz range.

8.3 High Pass Filters

This concept of reducing low frequencies has high relevance to producing the metal genre; particularly with a busy mix featuring fast, complex performances. Here, the aggressive and extensive use of high pass filters is essential for reducing boomy, uncontrolled, or unwanted low, or low mid frequencies, which have a tendency to accumulate and resonate. By reducing these low frequencies, the high frequencies, where the clarity of the instrumentation is associated, can be emphasised, resulting in these sounds being perceived as louder and more intelligible within the mix. Izhaki states that the use of a high pass filter “clears some space for the bass and kick, but more importantly it can add clarity and definition to the treated instrument” (Izhaki, 2008, p.243). For CM production, high pass filters can be used quite aggressively for the down tuned bass and guitar tonalities, and can be set above the fundamental, which can frequently be as low as 30.868Hz and 61.735Hz respectively. This is due to the ability of the brain to reconstruct fundamentals that have been removed or attenuated (Izhaki, 2008, p.244).

8.4 Separation Techniques

“When two or more instruments are fighting for the same frequency range, we can find it hard to discern one instrument from the other” (Izhaki, 2008, p.207). To provide the necessary definition and intelligibility for a CM production’s instrumentation, separation techniques therefore need to be employed. These techniques include focussing on attenuation rather then amplification, the use of high pass and low pass filters, avoidance of simultaneous amplification or attenuation of the same frequency on multiple instruments, the attenuation of frequencies on masking instruments rather than amplification of the same to the sound being equalised, and mirrored equalisation choices whereby the amplification of a certain frequency on one sound is mirrored with the attenuation of the same frequency on another relevant sound.

8.5 Compression

Compressors/limiters can also be used to make sounds more out in front. They do this by stabilising the sound so it doesn’t bounce around so much in volume. When a sound is more stable, our minds can focus on it more clearly, making the sound more present.  (Gibson, 2005, p.23)

Compression is the primary tool when retaining the stability and consistency of a sound within the context of the mix. When applied appropriately, compression can therefore contribute considerably to the intelligibility of the relevant instrumentation in the context of the overall mix.

8.10 Performance Attributes

The qualities of definition and intelligibility can also refer to performance attributes. Examples of which would be aggressive drum performance techniques, which will accentuate attack characteristics, and the use of down picking, which will normally create an aggressive element to the guitars attack characteristics.

9. Conclusions

  • This paper has presented the defining features of the genre’s high commercial standard of production as heaviness and sonic weight combined with definition and intelligibility of the instrumentation involved.
  • Relating specifically to heaviness and intelligibility, this paper has contextualised and characterised CM from a performance and tonality perspective.
  • This paper has highlighted the tonal and performance challenges and obstacles to achieving heaviness and intelligibility.
  • It has emphasised that the domains involved with perceived heaviness are frequency content, sound at source, density of sounds, perceived volume levels, and perceived consistency of volume levels, a minimal impact of spatial and depth characteristics in the form of ambience and reverb, transient design, vocal characteristics, as well as performance attributes. The paper has drawn attention to the salient points of each of these areas.
  • This paper has discussed the specific challenges to definition and intelligibility presented by CM tonalities and discussed sound at source, presence, high pass filters, separation techniques, compression and performance techniques as the relevant areas that can be controlled and manipulated to capture and present definition and intelligibility.

About The Author

Mark Mynett

University of Huddersfield, Department of Computing and Engineering


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