A SPECTROGRAPHIC ANALYSIS OF VOCAL
TECHNIQUES IN EXTREME METAL FOR
MUSICOLOGICAL ANALYSIS
Eric Smialek (1, 2)1
Philippe Depalle (2, 3)
David Brackett (1)
CIRMMT, McGill University, Montréal, QC, Canada
ABSTRACT1
Extreme metal genres such as death metal and black
metal force music analysts to seek alternative methods to
Western notation-based analysis, especially when one
asks what means of expression their vocalists may draw
from in order to seem convincing and powerful to fans.
Using spectrograms generated by AudioSculpt, a
powerful sound analysis, processing, and re-synthesis
program, this paper demonstrates a mixed application of
spectrograms and conventional music analysis to vocals
in two separate contexts: an a cappella recording in a
soundproof laboratory and a commercial recording with
a full band. The results support an argument for the
utility of spectrograms in revealing articulations and
expressive nuances within extreme metal vocals that
have thus far passed unnoticed in popular music
scholarship.
Western notation are obvious [10]. With this in mind,
the study of extreme metal presents something of a
disciplinary middleground in its foundations in popular
music studies and its incompatibility with Western
notation. Because extreme metal vocals place greater
importance on the timbral variations of vowels than on
pitch and harmony, methods of analysis that rely on
conventional notation do not reveal much information
about their expressive screams. Extreme metal vocals
thus provide an opportunity to analyze the role and
possibilities of spectrographic technology to reveal
information about musical expression in a genre of
music for which little to no analytical methods have
been established. Using real-time spectrographic
displays, this paper will demonstrate how spectrograms
can be useful research tools for scholars who require or
seek alternatives to notation-based analysis.
2.
1.
Popular music scholars have long insisted that details of
musical sound such as rhythmic and melodic inflections
or timbral characteristics are central in importance to
popular musicians and their audiences [1, 2, 3, 4].
Accordingly, some of the leading popular music scholars
such as Richard Middleton [1] and Philip Tagg [2] have
expressed criticism towards analyses of popular music
that overlook these features, often due to a reliance on
Western music notation. One alternative is to visually
represent sound through spectrograms, and it has now
been nearly thirty years since Robert Cogan made his
strong case for their utility to model musical sound in a
way that can account for melodic, rhythmic, or timbral
nuances [5]. Since then, despite the importance popular
music scholars have placed in these features, they have
rarely used spectrograms to study them. In the few
instances where they have appeared, such as [6],
reviewers have argued that spectrograms are superfluous
or have voiced a general distrust of analytical
technology such as spectrum photography or digital
signal processing of spectral imagery [7, 8, 9].
Such a distrust of musical spectrograms has not, of
course, extended to fields such as electroacoustic
composition and analysis where there exists an
epistemological tradition that has long supported the use
of music technology and where the limitations of
This research was greatly facilitated through funds from the
Social Sciences and Humanities Research Council (SSHRC)
and a CIRMMT Student Award.
1
(1): Musicology Area, (2): Centre for Interdisciplinary
Research in Music Media and Technology (CIRMMT), (3):
Music Technology Area.
_88
THE EXTREME METAL VOICE
INTRODUCTION
2.1. Basic Aspects of Vocal Production
To produce the vocal sounds characteristic of death
metal and black metal (as well as related sub-genres),
extreme metal vocalists pass air through the ventricular
folds (or “false vocal chords”) located a few millimetres
above the vocal folds (see [12] for anatomical details).
This allows extreme metal vocalists to achieve the large
spectral spread of energy visible in spectrograms.2
Extreme metal screams can be performed by either
inhaling or exhaling, resulting in two very distinct styles
of screaming. The different directions of air flow can be
thought of as akin to the linguistic distinction made
between voiced and unvoiced methods of articulating
consonants: when performing exhaled vocals, one’s
larynx vibrates, indicating that the vocal cords are
vibrating—rather forcefully—whereas this vibration
does not occur with inhaled vocals. This basic difference
has a profound effect on the overall sound quality
produced, the ease with which different phonetic
articulations can be made, the ability for a vocalist to
sustain a long scream, and the degree of strain put on the
voice.
Figure 1 demonstrates some of the acoustical
differences between inhaled and exhaled vocals. Here, a
volunteer extreme metal vocalist was asked to freely
2
A similar process is used in Mongolian throat singing
where singing voice formants are used to convey melodic
information [13].
(2, 3)
(1)
Figure 1. Some basic distinctions between extreme metal vocal techniques as demonstrated by a volunteer extreme metal
vocalist.
demonstrate these two types of voice. His inhaled vocals
are noticeably more agile with spectral energy
concentrated around a single focal point in the 1500–
2000Hz range (here and throughout this paper, the
horizontal grid is set to increments of 500Hz). In
contrast to that highly mobile focal point, the exhaled
vocals maintain a more balanced spectral distribution of
energy in the lower register of the spectrogram, moving
in comparatively small increments from one vowel to the
next in an almost mechanical fashion.
black metal, a sub-genre where a generally higher,
raspier voice predominates, vocalists will tend to raise
the frequency of their vowel formants past the levels that
would ordinarily correspond to their lyrics when spoken.
One way to think of each of these techniques, especially
those that lengthen the vocal tract, is to recognize that
the vocalists are physically mimicking the physiological
properties of a large beast: the ventricular folds produce
a spectral spread of energy that suggests an inhuman
sound source and the lengthening of the vocal tract
exaggerates the size of that source.
2.2. Vocal Tract Alterations that Imitate Inhuman
Sound Sources
Within these two basic categories of voice
production, vocalists may alter the length and shape of
their vocal tract to modify their voices in a wide variety
of expressive ways. To lengthen their vocal tract and
produce a lower sounding voice, vocalists may simply
lower their chin or conversely angle their chin upwards
to shorten the vocal tract length for a higher scream. It is
also possible to change the vocal tract length by raising
or lowering the larynx (or voice box), a process which
happens automatically in conjunction with the rounded
or spread lip shapes we use to articulate different vowels
(see Figure 2) [12].
Figure 2. George “Corpsegrinder” Fisher of Cannibal
Corpse rounds his lips to lengthen his vocal tract (left);
Dani Filth (Daniel Lloyd Davey) of Cradle of Filth
spreads his lips to make his vocal tract shorter (right).
This last point raises what is perhaps the most
important yet subtle technique that extreme metal
vocalists have at their disposal, the manipulation of
vowel formants. These vocalists will frequently sacrifice
the intelligibility of lyrical content in order to exaggerate
the sense of “heaviness” that can be perceived with
especially low vowel formants in death metal vocals. In
3.
SIGNAL PROCESSING AND RESYNTHESIS
USING AUDIOSCULPT
In order to investigate the aforementioned features of the
metal voice and their roles in music pieces, we decided
not only to perform spectrographic analyses, but also to
extract parameters that allow for a partial resynthesis of
key sound components in order to validate our
assumptions.
To explain, the following is a brief description of the
basic principles underlying AudioSculpt functionalities:
AudioSculpt generates a short-term Fourier transform
(STFT) representation of the sound.1 In order to
optimally display the sonogram image, STFT parameters
must be chosen including analysis window size and
shape, step size (that determines how the STFT fits over
the signal characteristics), and fast Fourier transform
(FFT) sampling. For each sound example in this study,
we used a Blackman window of size M=2400 with a
step size of M/8 and a number of channels equal to
4096. Once a satisfactory image is in view, it is ready to
be analyzed.
Qualitative judgments can be made based on the
obtained spectrographic image but more precise
measurements of vowel formant quality are also taken
by first synthesizing a new sound file based on the
original sound’s vowel formants using one of
AudioSculpt’s several spectral gain filters (in each case
during this study, the pencil filter tool). These filters
change the gain of certain frequency regions defined by
the user within the resynthesized signal. For this study,
1
The technical information offered here is based on [11].
_89
the regions to be filtered were defined according to a
computer-based analysis of the original sound file’s
partials. Specifically, AudioSculpt’s “Partial Tracking
Analysis” feature was used to track partials using
multiple breakpoint functions for each sinusoidal
component (a procedure that works with inharmonic
signals as well as harmonic ones). A new sound was then
created by amplifying the formant regions of the original
signal.
AudioSculpt’s diapason tool was then used to take
frequency readings from the synthesized partials. When
the tool is pointed at a particular place on the sonogram,
its frequency and amplitude are displayed, a
corresponding sine tone sounds, and a two-dimensional
spectral slice of the synthesized signal appears. This
procedure allows for an analysis of the original sound by
hypothesizing that certain components of it appear to be
important, resynthesizing those components, and closely
analyzing them.
4.
4.1. A Spectrographically-Informed Music Analysis
In addition to the spectrogram, Figure A1 also contains
phonetic and rhythmic transcriptions as well as
analytical annotations provided at the bottom of the
figure. As indicated by the rhythms given below the
spectrogram, the vocals fit neatly into a regular 4/4
meter, indicating that the vocalist kept a regular pulse in
marked contrast to his earlier performances discussed
above. Partly because of this rhythmic regularity, the
improvisation comes across as surprisingly organized, as
though it had been deliberately crafted.
An Impression of Tight Control
This impression likely results from several musical
features exhibited by the improvisation that are
1
An online appendix that includes larger images such as
Figure A1 can be accessed at
http://www.music.mcgill.ca/~depalle/ICMC2012/ICMC2
012Smialek.htm.
_90
note alternations between /ɚ/ (the r
“sure”) and /i/ (as in “heed”) in measure 12 are easily
ɹ
ɚ
column and, in the case of the one exception, the /iɚ/
A RECORDED IMPROVISATION
In order to investigate the features of extreme metal
voices presented in section 2 in a more musical context,
we asked a volunteer vocalist to perform a vocal
improvisation using whatever extreme metal vocal
techniques he wished. Given the somewhat artificial
performance environment—the room was virtually
devoid of reverberation and there were no instruments to
accompany the vocalist—the volunteer vocalist’s
improvisation shown in Figure A1 (see URL1), if not an
exact indicator of the performance decisions a vocalist
might make in a concert setting or full-band recording,
can be considered an accurate reflection of the kinds of
performance choices that are possible using inhaled and
exhaled voices and the variations in formant frequency
available with different vowel combinations.
4.1.1.
frequently invoked in discussions of basic musical
composition: the improvisation shows a clear binary
division into two roughly equal sections of music,
separated by a sudden change in dynamics (see the
dynamic markings at measure 7); each half contains a
recurring, slightly varying rhythm (labelled x and y) that
generally does not occur in the other half; and, following
the contours visible in the spectrogram, both divisions
exhibit an arch-like quality of intensification whereby
the vocalist’s screams steadily increase in volume and
high spectral frequencies (measures 2–4, 9–11) before
rapidly calming with quieter, lower vowels (measures 6–
8, 12–15). The total result is a sample of improvised
extreme metal vocals which demonstrates controlled
musical techniques in a regular manner, one that could
be heard as loosely narrative or rhetorical in the sense
that it creates regularly spaced climaxes, moments of
repose, and gradual variations. If there is a clear sense of
musicality to be found here, what can be inferred about
the vocal techniques used to achieve it?
4.1.2.
versatile rhotic (“r”) of Standard North American
Inhaled vs. Exhaled Vocals
Inhaled vocals in Figure A1 are shown by boxes around
the notation below the spectrogram, indicating that
exhaled and inhaled vocals are employed about equally
during the improvisation. Though aurally distinguishable
from exhales to those familiar with extreme metal
vocals, the distinguishing acoustical characteristics of
the inhaled vocals are not always immediately apparent
from the spectrogram (at least at the resolution given in
the example). What can be readily seen is a clear
difference in the highest regions of spectral energy
reached in measures 4–5 and 10–11. None of the
exhaled portions of the improvisation come close to this
region reaching upwards of 4000Hz, a circumstance
which indicates that only inhaled vocals allow the
vocalist to achieve the very wide spectral spread of
energy characteristic of these climactic moments in his
improvisation.
The vocalist also appears to have reserved at least
one of the vowels with especially high formant
frequencies for his inhaled voice. /æ/ (as in “had”), the
vowel most consistently present during these moments
of intense high spectral energy and a vowel with one of
the highest first formant frequencies, only occurs once as
an exhale (measure 2). Lastly, it seems that nearly all the
consonants with the exception of / ɹ / (and /p/ in measure
3) were reserved for exhaled vocals. Here, it would seem
that the closures of the vocal tract necessary to produce
some consonants prove too awkward to execute with the
steady “sucking” air flow used in inhaled vocals.
4.2. A Paradigmatic Analysis of the Improvisation
In order to arrive at an especially clear demonstration of
the primary role that certain phoneme combinations
played in the improvisation, Figure A2 provides a
ɹ
/ɹ /
ɚ
/ɹ /
/ɹ /
that there exists a consistency to the vocalist’s use of
of the measure with /ʊ/ (
“who”) from /a/ (as in “father”)
articulated /æ/ (as in “had”). It makes sense then that
upper jaw’s front teeth. One’s tongue quickly touches
paradigmatic analysis1 of the recording sample based
primarily on rhythmic identities and secondarily on
phoneme content. Although somewhat similar to a
musical score, the chart parses the music into segments,
usually spanning one measure each (measures are
indicated by circled numbers; segments spanning two or
more measures are enclosed within square brackets), and
distributes them horizontally to show difference and
vertically to indicate similarity. Musical time flows
downwards on the chart so that as new segments of
music occur in the recording, they appear in the chart
beneath one another whenever a portion of their rhythms
matches other segments (e.g. measures 2–6 and 11–12
have common rhythms for beats 3 and 4). Thus, a
continuously repeating piece of music would appear as a
single column while one that continuously introduced
new material would have its segments listed diagonally.
To add more columns of rhythmic identity and to
avoid cluttering them, the same segmented unit
sometimes appears more than once. Such is the case
with measures 1–2, which is shown as a single segment,
as well as measures 5, 9, 11, and 12 where each of these
segments reappear in new columns to the right. Inhaled
and exhaled vocals are indicated by different shades of
grey horizontal boxes but not in the case of reappearing
segments. Consequently, the chart can be followed in
real time along with the recording by reading only the
shaded segments, proceeding downwards from the topleft to the bottom-right corners. To draw attention to
areas of greatest interest, solid boxes outline regions that
show both identical rhythms and noticeably repeated
phonemes while dashed boxes indicate rhythmic
identities with little phonemic similarity.
4.2.1.
ɹ
Some Rhythmic and Phonetic Motives
The far-left column brings into relief how the vocalist
created a series of variations during the first half of the
improvisation (measures 1–6). Here, he has clearly
followed a pattern of varying his rhythms during beats 1
and 2 while treating beats 3 and 4 as a recurring
rhythmic motive (shown by the large vertical rectangle
around the common rhythms in the far left column).
Indeed, this recurring rhythm coincides with each of the
increases in spectral bandwidth that generate the archlike pattern visible in the first half of Figure A1.
On occasion, the vocalist has punctuated the last beat
of the measure with /ʊ/ (as in “hook”, marked to the
right of the column with arrows), a gesture that in each
case requires an elaborate motion of closing the jaw and
quickly rounding the lips when moving to /u/ (as in
“who”) from /a/ (as in “father”) or the similarly
articulated /æ/ (as in “had”). It makes sense then that
such an elaborate physical motion would be reserved for
a longer sustained rhythmic value and would punctuate
the final accent in a rhythmic motive. By contrast, the
1
One of the clearest introductions to paradigmatic
analysis available can be found in [14].
quicker sixteenth-note rhythms that occur as variations
in measures 3 and 6 are possible because the alveolar
closure made by the tongue when forming the consonant
/d/ can be executed quickly; similarly, the quick eighthnote alternations between /ɚ/ (the r-coloured vowel in
“sure”) and /i/ (as in “heed”) in measure 12 are easily
performed because they do not require elaborate jaw
motions, only quick shifts between lip and tongue
positions.2
4.2.2.
The Importance of /ɹ / Sounds
This last point raises one of the most conspicuous
consistencies observable throughout the recording
sample. The vocalist very frequently alternates between
/ɚ/ and /i/ sounds with both inhaled and exhaled vocals.
These phonemes occur for nearly all the articulations
contained within the solid box given in the left-centre
column and, in the case of the one exception, the /iɚ/
combination is merely displaced by a beat, and this is
marked by the arrow in the left-centre column. The
versatile rhotic (“r”) of Standard North American
English is especially worthy of emphasis here for both
the acoustical and physiological advantages it offers the
vocalist. This sound does not require a stoppage in air
flow so it can be used as a vowel (e.g. /ɚ/ as in “fir”) or
as a consonant (e.g. /ɹ / as in “rapid”). As a result, it is
especially suited to the physiological difficulties of
articulating consonants with inhaled vocals (note again
that nearly all of the other consonants are exhaled).
Because it can be articulated with a continuous air flow,
the /ɹ / can be used to slightly alter vowels. Specifically,
when a vowel is rhotacized, i.e. coloured by an /ɹ /, the
third formant becomes lowered [15].
Even if this third-formant lowering is not as directly
tied to an impression of heaviness as the lowering of the
first two formants, it nevertheless provides a way for the
vocalist to create variety and, on a social-perceptual note
with regards to paralanguage, it seems more than a
coincidence that the /ɹ / sound is often used to imitate
the snarls of wild beasts.3 Having drawn a number of
inferences as to why certain patterns appeared in the
improvisation, the strongest and most basic point here is
that there exists a consistency to the vocalist’s use of
particular phonemes in such a way that they seem
fundamental to the most salient musical features of the
improvisation.
2
The alveolar ridge is the sloping region located by the
upper jaw’s front teeth. One’s tongue quickly touches
this plain to stop the flow of air through the vocal tract
when producing the consonant /d/ [15].
3
Paralanguage can roughly be understood to include all
forms of non-verbal communication. These can include
facial expressions, vocal utterances such as grunts and
sighs, as well as prosaic and timbral modifications to
ordinary speech that shade meaning [16].
_91
5.
AN EXCERPT FROM “THE VOWEL SONG”
Framed as a public service promoting literacy, “The
Vowel Song” by death metal band Zimmer’s Hole
begins with vocalist Chris Valagao reciting the vowels
of the alphabet (henceforth “letters” to distinguish from
phonetic vowels) in long sustained screams, harmonized
by three guitars in homorhythm (see Figure A3). The
slow punctuations of each homorhythmic attack,
combining voice, low power chords (shown only as
roots in the example), and two harmonized lead guitars,
not only lend a certain satirical grandiosity to song, they
also help to create the sensation of Valagao’s unpitched
screams possessing a kind of melody, drawn by a precise
control of formant frequency locations.
5.1.1.
Formants in Flux
Although it may not be immediately evident in the
spectrograms given here, there is quite a great deal of
variation to the formant frequencies used in the example.
In order to illustrate this variation, Figure 3 plots the
position of each letter that Valagao screams within
vowel space, i.e. a graph which plots vowels according
to the frequency of the first formant on the y-axis and
second formant on the x-axis. Of course, some of the
letters Valagao screams are actually diphthongs or
triphthongs. Accordingly the most steady-state vowel
within each letter is identified with a dot on the graph
and arrows leading up to or away from it depending on
how the phonetic transitions occur. To illustrate an
example, Valagao’s screamed letter “u,” represented by
plot #5, is performed in such a way that it traverses
vowel space beginning near /ɪ/ (as in “hit”), reaching its
most steady-state point near /ɑ/ (as in “harm”), and
finally moving towards the lower formant frequencies in
between /ʊ/ and /ɔ/ (as in “hook” and “caught”
respectively). It becomes clear how much formant
variation is involved in this song introduction from only
examining the steady-state plot points, let alone taking
into account all the quick diphthong transitions indicated
by the arrows.
5.1.2.
Interactions between the Voice and Guitar
If these changes in formant frequency are compared with
the pitch contour of the guitar parts (which move in
parallel motion), a surprising correspondence appears
between the guitars’ changes of pitch direction and the
movements of the first formant. As the first letter
changes to the next, the lower formant decreases in
frequency paralleling the descent of the guitars (see the
“changes of direction” arrows in Figure A3). With the
next letter, the lower formant reverses direction just as
the guitar does. This pattern of alternating upwards and
downwards directions, shared between the guitars and
the voice’s first formant, continues until the guitars and
voice break the homorhythm. What’s more, there is an
even stronger correspondence between the highest lead
guitar part and the voice’s first formant movements. This
_92
is shown in Table 1 (see next page) which compares the
high lead guitar melody with the first formant of each
vowel at its point of greatest stability and sustain (the
dotted points in Figure 3). Both are shown as frequency
values in Hz and in terms of pitches that correspond to
those frequencies. A comparison of these pitch values
(including their octave position) reveals a striking
relationship. With a margin of about one semitone above
and below the upper guitar part, the voice’s first formant
parallels the exact contour of the guitar part.
Figure 3. Formant positions from the opening of “The Vowel
Song” plotted in vowel space [17]. Each letter that Valagao
screams is assigned a number. Arrows indicate phonetic
transitions before and after a vowel is stabilized and sustained.
Taking into consideration that there is usually a
frequency range of around 100Hz over which each
formant’s energy is significant (the values in Table 1
sample the average frequency for the first formant) and
that the voice is in rhythmic unison with the guitars, it
does not seem far-fetched for a listener to perceptually
connect the guitar melody and the formant movements,
thereby imagining a kind of melodic motion assigned to
a series of unpitched screams. Even after the
homorhythm breaks off, one can discern further
frequency-oriented connections between the voice and
its surrounding musical contexts. As the vocalist finishes
preparing the last letter by screaming the words “and
sometimes,” a diving upper harmonic merges with his
third formant beginning with the onset of the final letter
Y. In this brief intro to “The Vowel Song,” the widely
taken for granted division between timbre and pitch
appears especially blurred.
6.
CONCLUSION
Having observed extreme metal vocal techniques in both
a relatively controlled recording session and at work in a
commercial studio recording, it should now be clear that
the extreme metal voice is far from the simplistic
percussive device that it is often assumed to be. If such
–
–
–
–
–
EXCERPT FROM “THE VOWEL SONG”
assumptions are in no small part the result of deeply
entrenched habits of describing vocal music primarily in
terms of pitched melodies, the extreme metal voice can
serve as an invitation to approach the study of musical
expression in new ways. Having taken an
Upper Melody (Gtr 1)
First Formant
No. 1 – A
C6/1050Hz
C#5/540 Hz
No. 2 – E
G5/780 Hz
G4/380 Hz
interdisciplinary approach to the extreme metal voice,
the results of this paper support ongoing arguments for
the musicological utility of spectrograms in drawing
attention to subtle means of musical expression that can
easily be overlooked.
No. 3 – I
Eb 6/1240 Hz
F5/700 Hz
No. 4 – O
C6/1050 Hz
B4/510 Hz
No. 5 – U
Eb 6/1240 Hz
E5/650 Hz
Table 1. A comparison of frequency values between the highest lead guitar’s melody and the first vocal formant in its point
of greatest stability.
7.
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