Source Signals is an album with music I recorded between 1981 and 1985. The album showcases a transition from pop-oriented guitar tracks to experiments with electronics in which the guitar was the main sound source. Several bass guitar overdubs and one guitar overdub were made before the album was released in 2019.
My rediscovery of these tracks and the decision finally to release them also triggered a renewed interest in the guitar as a musical instrument. Electric and classical guitars have a huge sound potential and they are a pleasure to play.
After the LP Source Signals was released, I had been playing guitar at home almost on a daily basis, initially without a concrete plan. Gradually, however, an idea developed to compose an acousmatic multichannel work in which guitar playing would be the only source. I deliberately say ‘guitar playing’ and not just ‘guitar sounds’, because I’m interested in guitar sounds produced with musical intentions, expressed through playing skills that are developed through practice. Nevertheless, these ‘played’ sounds still had to function in a larger, abstract musical construction. So, the question was: where lies the threshold between listening to recorded guitar playing and the perception of a higher-level musical construction consisting of played guitar sounds?
These considerations led to the following decisions:
- Only individual tones would be played and recorded.
- Such tones (sometimes more than 1000 for a single material group) would always be played with a view to their place in a preconceived form.
- Every recording would be preceded by a long warm-up period, so that tones would be played with confidence and expression.
- No extended techniques would be used.
- No transformations, or only modest ones, would be applied to the recorded sounds.
- The recordings should have clear references to ‘known’ guitar sounds and genres (rock, psychedelia, classical).
- It should be evident for the listener that it would be impossible to perform the constructions in real time (speed, spatial distribution, timbre/pitch combinations, density).
- A pitch system based on twelve-tone series would be used throughout the piece for most material groups.
- In contrast to the material groups based on twelve-tone series, some would be based on harmonic series (overtones), and some on a single pitch in various octaves.
- Each section in the piece would be dominated by a specific sound type.
- The piece would have an album character, in which the order of the various sections would be determined only at the very end.
Even when the guitar playing is very recognisable, it is always clear that the sounding result could never have been played in this form. For example, as will be explained below, the eight-part chords of Material Group 1 are unplayable merely because of their range. In addition, a chord might contain more than one pitch played on the same string. Also, the eight pitches of each chord are distributed in different ways across eight loudspeakers, added to which is the high speed with which some chords succeed each other. Similar arguments apply to Material Group 3.
In Material Groups 4 and 5, as will be explained, sequences of overlapping electric guitar sounds are used, each sound having a different timbre drawn from the 144 different combinations of the pickup selector on the guitar, the amps and effects units. The individual sounds are also distributed here over the loudspeakers.
In Material Group 9, the sound of a Fender Stratocaster is unmistakable. However, once again the chords exceed playable range. At the same time, the partly overlapping chords are recorded with different combinations of pickups and with individual pitch bends.
In the following chapter, much attention is devoted to the explanation of a twelve-tone system which is used in many of the material groups. Pitch organisation primarily applies to instrumental music, where pitch is usually a primary parameter. With the exception of some percussion instruments, all musical instruments are intended to play pitches, and listeners have a preoccupation with this parameter.
Because in electronic music the central point is not the pitch of musical instruments but the timbre of all kinds of imaginable sounds, pitch structures are more often avoided than applied. After all, the listener’s attention will be distracted precisely by the aforementioned preoccupation with pitch from the actual focus of electronic music, its timbre.
For this reason, instrumental and electronic music have historically been thought of as separate categories, and there is much electronic music where sounds with a clearly discernible pitch do not occur at all. However, the boundaries between these categories have become rather blurred, not least because instrumental music is nowadays more often heard through loudspeakers than in the concert hall. In addition, much popular tonal music is produced entirely with electronic musical instruments, and there is much composed instrumental music in which timbre – for example through the use of extended techniques – is more prominent.
I myself have composed much electronic music in which pitch organisation plays no significant role. On the other hand, I am convinced that when sounds with a clearly perceptible pitch do occur in a piece, this pitch – precisely because of the degree to which this aspect of the sounds demands attention – must be consciously structured. Pitch cannot be left to its own devices, if only because in electronic music, accidental sound constellations that could evoke memories of music based on functional harmony should at all times be avoided.
And that is precisely why I find the application of twelve-tone series so attractive. Its use offers the possibility of taking a structural approach to sequences and compositions consisting of clearly pitched sounds, as well as that of excluding harmonic clichés. In addition, through serial technique, the pitch organisation can be incorporated into other structural aspects. In that regard, it is pertinent to note here that the chapter in Nielinger-Vakil’s book Luigi Nono: A Composer in Context from which the magic square of figure 2 comes is called “Towards Spatial Composition”.
For me, the essence of serial technique is not, as is often claimed, that it makes use of numbers. The essence is that two extremes are determined and that the space between them is systematically explored. Serial technique is therefore essentially spatial, and the numbers act as a practical aid in this regard. The fact that the application of serial technique leads to music in which sound sources are actually distributed in physical space is therefore not a coincidence but a consequence.
This also explains why tables and matrices are so often used in the descriptions of the production of the material groups for Source Signals 2. These provide the material groups with an underlying structure, which not only ensures cohesion within a material group but also constitutes an investment in the material groups, which pays off as well when (parts of) these groups are combined into larger constellations. The same pitch sequences and numerical constructions underlie these material groups, so that when they (partially) overlap they enter into relationships with each other that are meaningful to me, and, I assume, also to the listener.
In the summer of 2017, I read Carola Nielinger-Vakil’s previously mentioned book Luigi Nono: A Composer in Context. By then I was already familiar with Nono’s use of all-interval series. An all-interval series is a special case of a twelve-tone series, in which not only all twelve chromatic pitches, but also all intervals from minor second to major seventh are used once.
What was new to me was Nielinger-Vakil’s description of a magic square, in which the all-interval series is permutated by a permutation row (a row of numbers that determine the position of the pitches of the previous series in the next one). In figure 2, the all-interval series with decreasing intervals (major 7th, minor 7th, major 6th, minor 6th, 5th, augmented 4th, 4th, major 3rd, minor 3rd, major 2nd, minor 2nd) is shown at the top line. The twelve-tone series of lines 2 to 6 in the magic square are the result of the permutation row 11, 8, 1, 6, 9, 10, 3, 4, 7, 12, 5, 2. The twelve-tone series on lines 7 to 12 are retrogrades of lines 6 to 1. Each column is a twelve-tone row as well.
I became intrigued by this method and asked myself if it would be possible to take an all-interval series with increasing intervals as a starting point, and find a permutation row that would result in a chromatic series of pitches after eleven permutations.
In the end I found more than one way to do this, but so far I have only made use of the following two permutation rows: 8, 9, 7, 6, 10, 5, 11, 4, 12, 3, 1, 2, which results in a descending chromatic series after eleven permutations, starting at E and ending at F (see figures 3 and 4); and 11, 12, 10, 1, 9, 2, 8, 4, 7, 3, 6, 5, which results in an ascending chromatic series after eleven permutations, starting at B and ending at B flat (see figures 5 and 6).
The three broken chords notated next to each series are created by taking the first pitch of the series in the lowest octave (of my system) and then the three subsequent pitches with intervals of at least a major sixth.The scales in figures 7 and 8 are derived from the three broken chords of each series by writing their pitches from the lowest one to the highest.
The following (emulated) equipment was used to produce the sound material:
- Ibanez L6-s electric guitar (a 1970s copy of a Gibson L6-s) with a six-position pickup selector, offering six different, distinctive sounds.
- Fender American Deluxe Stratocaster electric guitar with two noiseless single-coil and one humbucker pickup, offering 10 different sounds.
- An Alhambra CS LR CW E1 acoustic guitar with nylon strings and built-in piezo pickup.
- A Fender Squier Jazz Bass with active pickups.
- Fender 1960s Pro Reverb amplifier (emulated).
- Fender 1964 Vibroverb amplifier (emulated).
- Fender 1967 Twin Reverb amplifier (emulated).
- Vox 1966 AC 30 Top Boost amplifier (emulated).
- Ross compressor (emulated).
- MXR Phase 90 (emulated).
- Ibanez TS-808 Tube Screamer (emulated).
- Boss CE-1 Chorus Ensemble (emulated).
- Maestro Echoplex EP-3 (emulated).
- Electro-Harmonix Deluxe Memory Man (emulated).
- Vox V846 wah (emulated).
- Univox Uni-Vibe (emulated).
- Lesley rotary speaker (emulated).
- Neumann U87 microphone (emulated).
- AKG C451 B microphone.
- RME Fireface 800 audio interface.
- Avid Eleven Rack guitar interface.
- Pro Tools 10 HD software/hardware.
- Capybara 320 sound computation engine with Kyma X software.
The material groups for Source Signals 2 are described here in the order in which they were produced. This order is different from the order in which these groups appear in the final composition.
Recordings of an acoustic guitar with nylon strings were made while playing chromatic pitch series on each string. The output of the built-in pickup was combined with that of a condenser microphone placed closely to the strings. All tones were recorded sustained as well as stopped.
- E-string, tuned to C: C (open string) to E flat (3rd position).
- E-string: E (open string) to E (12th position).
- A-string: A (open string) to A (12th position).
- D-string: D (open string) to D (12th position).
- G-string: G (open string) to G (14th position).
- B-string: B (open string) to E flat (16th position).
- E-string: E (open string) to B (19th position).
- E-string, tuned to F sharp: C (18th position) to C sharp (19th position).
18 chords of 8 stopped tones were assembled according to the chords of twelve-tone series 1-1 to 12-1 (see figures 3 and 4).
Subsequently, these 18 chords were placed in a structure in which rapid successions of 2, 3 and 4 chords occur as well as single chords.
- Chord 1 distance to next chord 10 seconds.
- Chord 2 distance to next chords 8 seconds.
- Chords 3–4 distance 300 milliseconds, distance to next chords 7 seconds.
- Chords 5–6–7 distance 200 milliseconds, distance to next chords 11 seconds.
- Chords 8–9–10–11 distance 100 milliseconds, distance to next chords 9 seconds.
- Chords 12–13–14 distance 200 milliseconds, distance to next chords 6 seconds.
- Chords 15–16 distance 300 milliseconds, distance to next chord 12 seconds.
- Chord 17 distance to next chord 5 seconds.
- Chord 18
This is the second material group that was produced. However, it was revised several times during the production of the other material groups. It was clear from the start that it would take an important place in the large form of Source Signals 2.
A selection of 111 sustained single tones was made from the acoustic guitar recordings that were described earlier (see Material Group 1) and analysed in Kyma. The 72 analysis files were resynthesized according to a table with 72 presets, resulting in 72 quadrophonic sound files. The pitches follow twelve-tone series 1-1 to 6-1 (see figure 3).
The structure of Material Group 2 consists of single tones and combinations of 2 to 6 tones. In the case of tone combinations, the twelve-tone series progresses vertically. The beginning of each twelve-tone tone series was emphasised by an additional bass tone. Finally, the last tone or tone combination of a series was reversed, resulting in crescendi that lead to the attack of the first tone(s) of the next series.
From the recordings of an acoustic guitar with nylon strings as described in Material Group 1, a selection was made of sustained sounds according to the scales derived from the chords of the twelve-tone series 1-2 to 12-2 (see figures 5 and 6). The tones for 10 of these scales (2 to 11) were then sequenced according to the rhythmical/spatial patterns originally designed for my composition Serenade (2017). The tones for scales 1 and 12 appear as twelve-tone chords.
For these material groups, the Ibanez L6-s electric guitar was used to record a large number of single tones with 6 pickup and 24 (emulated) amplifier/sound-effect combinations, resulting in 144 different groups of guitar sounds. In contrast to the other material groups, of which the pitches are either based on twelve-tone series or harmonic series, all tones are now A on various strings and in various octaves.
- A1: Fender 1960s Pro Reverb amplifier.
- A2: as A1 but with Boss CE-1 Chorus Ensemble after amplifier.
- A3: as A1 but with MXR Phase 90 before amplifier.
- A4: combination of A2 and A3.
- B1: Fender 1964 Vibroverb amplifier.
- B2: as B1 but with Ross compressor before amplifier.
- B3: as B2 but with Boss CE-1 Chorus Ensemble after amplifier.
- B4: as B3 but with tremolo on amplifier.
- C1: Fender 1967 Twin Reverb amplifier.
- C2: as C1 but with spring reverb on amplifier.
- C3: as C2 but with Univox Uni-Vibe phaser before amplifier.
- C4: as C3 but with Lesley rotary speaker after amplifier.
- D1: Vox 1966 AC 30 Top Boost amplifier.
- D2: as D1 but with slow vibrato (tremolo) on amplifier.
- D3: as D2 but with Ross compressor before amplifier.
- D4: as D3 but with MXR Phase 90 after compressor and Electro-Harmonix Deluxe Memory Man after amplifier.
- E1: as D4 but with Ibanez TS-808 Tube Screamer after MXR Phase 90.
- E2: Vox 1966 AC 30 Top Boost amplifier (maximum level).
- E3: as E2 but with compression plugin after amplifier.
- E4: as E3 but with Vox V846 wah before amplifier.
- F1: Fender 1967 Twin Reverb amplifier (maximum level) with pre-delay/reverb plugin after amplifier.
- F2: as F1 but with Univox Uni-Vibe phaser before amplifier.
- F3: as F2 but with tremolo on amplifier.
- F4: as F3 but with Ross compressor before Univox Uni-Vibe and Maestro Echoplex EP-3 before pre-delay/reverb plugin.
All recordings were made with an emulated Neumann U87 microphone.
For Material Group 4, 12 sequences were made of 12 different tones, whereby the guitar sounds were selected from groups A1–F4 according to a matrix (see figure 18). Within each sequence, the sounds appear at regular distances of 500 milliseconds while following a spatial distribution pattern (see figure 19).
Later on, another 12 similar sequences were made, again on the basis of the matrix of figure 18, but this time, different sounds from groups A1–F4 were selected.
What becomes clear from the list of amplifier/sound-effect combinations shown earlier, is that the distorted guitar sounds appear in E1–F1, whereas A1–D4 are relatively ‘clean’. Eventually it was decided to make 2 groups of 12 sequences, in such a way that the distorted sounds only occur in the second series of 12 sequences.
- Group 1: sequences 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23
- Group 2: sequences 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24
In the end, only 6 sequences of group 1 and 3 sequences of group 2 were used in section 5.
While recording the tones for Material Group 4, it was coincidentally discovered that with some pickup/amplifier/sound-effect combinations, long sustained sounds could be made by exciting the string with the finger on the fretboard and/or creating feedback by approaching the loudspeaker with the guitar at high monitoring levels. These sustained sounds were recorded as well and resulted in Material Group 5.
A selection of sustained sounds was made and provided with fade-ins and fade-outs, after which they were placed in a construction of 8 stereo layers, resulting in a continuous wall of sound with varying tone colours.
36 sustained electric guitar sounds from Material Group 5 were selected and analysed in Kyma. The analysis files were then resynthesized with a Kyma patch with quadrophonic output, in which each channel has a different pitch and different duration (time stretch/compression) according to the following table:
The 36 quadrophonic sound files were distributed over 16 tracks in such a way that every sound file starts at half the duration of the preceding one. In the second and final version of this material group, combinations of two quadrophonic sound files were made before they were placed in an overlapping form of 24 tracks, as a result of which the total duration became considerably shorter.
From each of the bass guitar’s four strings, natural harmonics above the 2nd, 3rd, 5th, 7th, 9th, 10th, 12th, 15th and 17thfret were played and recorded. A quadrophonic granular sound of 50 seconds was then made of each of these 36 tones, whereby the buffer for the grains was read directly after the attack, so at a point in the sample where the noise of the transient no longer sounds but the harmonics are still clearly present.
Some of the granular sounds had too much mid-low frequencies and were therefore filtered with a quadrophonic channel-strip plugin in Pro Tools.
The 4 quadrophonic sounds from the same position on the neck but from different strings were then synchronised, so the granular sound from the harmonics above the 2nd fret from strings E, A, D and G, etc., resulting in 9 16-channel granular sounds.
These 9 sounds were mixed to 8 channels and recorded, during which some filtering with the channel-strip plugin was applied again. The 8-channel mixes were then placed in the following order with overlaps and volume envelopes: sounds from the 12th fret, 7th fret, 5th fret, 9th fret, 3rd fret, 15th fret, 17th fret, 2nd fret, and 10th fret.
For this group, the 36 harmonics (9 from each of the bass guitar’s 4 strings) that were used for the granular synthesis sounds of material group 7 were analysed in Kyma.
The 36 analysis files were resynthesized with a quadrophonic resynthesis patch in Kyma with 36 presets (see figure 22). Each preset contains 4 transpositions and 4 durations. The transpositions of each set of 3 presets together form a twelve-tone series; 12 sets of 3 presets make a complete walk through twelve-tone series 1-1 to 12-1.
The quadrophonic resynthesized sounds were then combined into groups of 3. Within each group, the sounds overlap partially, whereby the next sound starts at the end of the shortest tone within the previous quadrophonic sound.
The 12 groups of 3 quadrophonic sounds were divided into 4 subgroups of 3.
- Subgroup 1 occurs in section 4.
- Subgroup 2 occurs in section 6.
- Subgroup 3 occurs in section 8.
Together with the resynthesized tambora sounds of Material Group 11, these sounds form the backbone of Source Signals 2.
The following (emulated) equipment was used for Material Group 9:
- Fender Stratocaster with Switch S1 pressed.
- Ross compressor.
- 1964 Fender Deluxe Reverb amplifier.
The tones of the (broken) chords based on twelve-tone series 7-1 to 12-1 were played one by one. Each tone was played four times with different pickup selector positions (2, 3, 4 and 5) and individual tone bends. Tones that fell outside of the range of the guitar were played after re-tuning (lower low E-string, higher high E-string). Six structures in which the chords have different spatial positions were then made according to the following schemes:
Synchronisations 1 to 3 appear in section 2, 4 to 6 appear in section 6.
For this material group, a Fender Stratocaster was played with an e-bow.
- E-bow in position H (harmonic).
- Stratocaster pickup selector in position 1 + S1 switch.
- Dyn3 compressor plugin.
- Univox Univibe phaser (emulated).
- 1967 Fender Twin Reverb amplifier (emulated).
- Neumann U87 microphone (emulated).
Tones were played and recorded according to the twelve-tone series 1-1 to 12-1. The 144 tones (12 tones from 12 series) were edited from the recordings as separate sound files and then analysed in Kyma. The 144 analysis files were resynthesized with a Kyma patch with quadrophonic output, in which each output has a different duration. These durations were stored in 72 presets according to the table of figure 12.The resynthesized quadrophonic sounds were then synchronised in 3 groups of 4, according to the following scheme:
A total of twelve synchronisations were made (one for each of the twelve-tone tone series 1-1 to 12-1). Synchronisations 1 to 4 were used in section 1, synchronisations 7 to 9 in section 8.
Knocks on various places of the acoustic guitar’s body were recorded with an AKG C 451B condenser microphone and the guitar’s built-in piezo pickup, both connected directly to the RME Fireface 800 interface. The two signals were recorded in Pro Tools on separate channels.
The six strings were tuned as follows (low to high): Es–As–Cis–Fis–B–E.
24 recordings were made of the tambora sounds with a capo on the first, second, third, fourth position, etc. with undamped strings (for the eleventh and twelfth position, a full bar was used because the capo wouldn’t fit the guitar’s neck at these positions). At each position, one recording was made during which the guitar’s body was knocked with the thumb, and another one with the fingers.
Between 6 and 10 sounds from each two-channel recording were selected and bounced to a mono track, during which the microphone signal was mixed with the built-in pickup.
A second selection was then made of 3 sounds from every recording, resulting in a group of 72 sounds that were analysed in Kyma, resulting in 72 analysis files.
For the resynthesis of these 72 files, a Kyma patch was used with quadrophonic output, in which each channel has a different pitch and different duration (time stretch/compression). The pitches and durations were stored in 36 presets according to the table in figure 22. The 72 quadrophonic resynthesized sounds were then combined into 18 sound groups according to the following table:
It is relevant to mention here that in flamenco music, tambora sounds stand as a symbol for heartbeats. Due to the regular appearance of the resynthesized tambora sound groups in Source Signals 2, one could say indeed that they are the heartbeat of the composition, be it a very slow one.
As already explained in the introduction, the large form of Source Signals 2 was conceived as an ‘album’: the material groups were composed first, after which the large form was assembled.
Two parts consist of only one material group, the other parts contain combinations of material groups. To emphasise the connection with the vinyl release Source Signals (1), the parts of Source Signals 2 are called “Signal 7” to “Signal 14” (“Signal 1” to “Signal 6” are on the Source Signals LP, together with “Source 1” to “Source 10”).
1. Signal 7 00:00–03:18 Material Groups 10 and 11.
2. Signal 8 03:18–04:31 Material Groups 9 and 11.
3. Signal 9 04:31–06:51 Material Group 7.
4. Signal 10 06:51–09:54 Material Groups 1, 3, 8 and 11.
5. Signal 11 09:54–16:02 Material Groups 4 and 5.
6. Signal 12 16:02–18:45 Material Groups 8, 9 and 11.
7. Signal 13 18:45–23:12 Material Group 2.
8. Signal 14 23:12–27:43 Material Groups 6, 8, 10 and 11.
In the introduction of this text I explained how the idea arose to compose a piece based on self-played guitar sounds, and what the starting points were for its realisation, with the additional requirement that these played sounds should always exist in a functional relationship to the composition’s formal design, alongside an exploration of where the boundary lies between listening to recorded guitar playing and the perception of a higher-order musical construction built up from played guitar sounds. This boundary was constantly monitored during the creation of the material groups, even if it was not really mentioned in the descriptions. However, it is not difficult to recognise the decisions listed in the introduction in my descriptions of the material groups.
In the meantime, Source Signals 2 was premiered in the Royal Conservatoire’s Arnold Schoenbergzaal on 8 December 2020 for a small but refined audience, due to coronavirus restrictions. The hall was equipped with two eight-channel loudspeaker systems: one wide circle of eight Meyer Sound UPAs with four additional subwoofers, one in each corner of the hall, and a narrower circle of eight small Amadeus PMX5 speakers with one small subwoofer each . By varying the levels between these two sets of eight speakers, a big, symphonic sound that included the hall’s resonances could be created when appropriate (for instance in sections 3, 5 and 7) whereas at other moments, a more intimate, less reverberant acoustical situation could be created by adding the small speakers that were positioned more closely to the listeners or by using them exclusively (for instance in sections 4 and 8). Of course, different loudspeaker configurations can be used to present Source Signals 2 (and my other eight-channel compositions), as long as there is a minimum of eight speakers surrounding the audience at more or less equal distance, and as long as additional speakers are combined in groups of eight too. The balance between the eight channels of the composition should stay intact at all times.
 Carola Nielinger-Vakil, “Towards Spatial Composition” in Luigi Nono: A Composer in Context (Cambridge: Cambridge University Press, 2015), 85–122.
 This system for pitch organisation was also used in my composition …ritroverai qualcosa… (2017).
 The e-bow is an electronic device that uses a pickup in an inductive string driver feedback circuit, including a sensor coil, driver coil, and amplifier, to induce forced string vibrations. The e-bow produces a sound reminiscent of using a bow on the strings (https://en.wikipedia.org/wiki/EBow).
 This Amadeus speaker set was custom-made for the Groupe de Recherches Musicales (GRM) in Paris and then produced for a second time for the Institute of Sonology in 2013.
 A binaural recording of this concert was made by Justin Bennett.