Tiptop Audio Z-DSP cartridge - Grain de Folie
Granular effects fir the Z-DSP
Granular Synthesis uses small slices of sounds (‘grains’) to compose new sounds from existing
material. By combining multiple grains of diering lengths, amplitude, pitch and speed creates
very characteristic sounds of modern music.
Xenakis claims to have invented the technique and indeed his ‘Analogique A-B’, composed of
tiny tape splices of pure tones, is credited as the rst piece of granular music in 1959. Tape
editing proved extremely time consuming, but by the 1970s digital processing could take the
place of tape splicing. Curtis Roads dove into the early computer based granular synthesis and
made some of the classic techniques known through his recordings, teaching and texts like
‘Microsound’. Today, most computer audio programs have some sort of granular synthesis
engine or plugin. Dr. Richard Boulanger has used granular synthesis in CSound to great eect
and he is also a beta tester for this card.
The French phrase for the cartridge is "Grain de Folie" which could be translated as "seeds of
madness", but in French "grain" also translates to "grain", and "madness" evokes the strange
disassembling/reassembling granular process. Also, "avoir un grain de folie" is a typically
French expression to describe people behaving in a non conventional way, thus a tting play on
Granular processing requires a block of memory to hold digital samples for playback, and the
Z-DSP has one second of memory for the audio used in processing. From this audio buer the
grains will sample smaller sections for playback.
The number of grains in the process determine how dense the overall output sounds. These
programs have 3, 4 or 6 grains for playback. Each grain plays from a random point in the audio
buer and have an independent envelope controlling their duration. The envelope time is the
‘grain size’ parameter in many of the programs.
In the context of the Z-DSP, the FV1 (the DSP brain) is really not designed for grain synthesis
(due to technical choices like a "circulating" delay memory, and the lack of indirect memory
access), but the chip also has other design niceties that help overcome its limitations…
This cartridge implements a simple and customised granular synthesis with a limited number of
grains, and parameters that mainly control the size of grains and their positions in the sample.
One nice aspect of the Z-DSP is that it uses live inputs (granular synthesis is usually based on a
pre-recorded sample), so it can disassemble live input and reassemble it in real-time into a
dierent order resulting in a (usually !) nice sonic transformation of both texture and the
All programs have a random grain position. The left control and the CV input have always the same function, activating one of three different states:
- Off = live processing of audio which is fed constantly into the delay.
- 1-25 % = Freeze buffer. No audio is fed into the delay.
- 26-100 % = processed audio is fed back to the input. The higher the value the more feedback. Glitches happen at high settings.
- Four spread grains #1: control of length and position. Two grains are output left and two right in the stereo field.
- Four spread grains #2: control of length and position. All grains have the same size, reducing the stereo width.
- Pitch modulated grains #1. Control of each grain's pitch by LFO. Two grains are emitted on left channel, two other on the right one.
- Pitch modulated grains #2. Control of each grain's pitch but with a lower amount than Program 3. Two grains to the left, two to the right.
- Three pitches grains. Control of pitch shifting (the same fixed amount for all grains). One grain to the left, two to the right and one circulates in the stereo field.
- Six grains in Stereo. Two grain size controls, each one for three grains, generating different textures / rhythms. Three grains are output to the left and three to the right.
- Three flying grains. Control of size and panning rate. Panning creates a stereo spread.
- Three modulated grains. Control and modulation of grain size, varying the texture. Output in stereo.