The situation — You want an instrument that can play any number of oscillators, determined by a p-field value in the score. The problem — Unit generators cannot be dynamically created in an instrument with a simple loop. One possible solution — Multiple events can be generated in a loop, with each event triggering an oscillator-based instrument.
The Csound file Deep_Synth.csd provides an example of how to dynamically generate oscillators using the compound instrument technique. A compound instrument is two or more instruments that operate as a single functioning unit. This particular compound instrument is built from two instruments: DeepSynth and SynthEngine. SynthEngine is, you guessed it, the synth engine, while DeepSynth is a player instrument that generates multiple events for SynthEngine using the opcodes loop_lt and event_i:
i_index = 0
event_i "i", $SynthEngine, 0, idur, iamp, ipch, iattack, idecay, ipan,
irange, icps_min, icps_max, ifn
loop_lt i_index, 1, ivoices, loop_start
If you are wondering why we can’t just place a unit generator, such as oscil, inside of a loop, read Steven Yi’s articles Control Flow Pt I and Pt II. Pay special attention to the section IV. Recursion – Tecnical Explanation near the end of Pt. II. Not only does Mr. Yi do an excellent job explaining these technical reasons, but he also provides another applicable solution for creating multiple unit generator instances utilizing recursion and user-defined opcodes.
The instrument SynthEngine uses a single wavetable oscillator, an amplitude envelope and the jitter opcode to randomly modulate frequency. A single instance of DeepSynth can generate multiple instances of SynthEngine. DeepSynth can generate a single instance, or 10,000+. Users have control over the depth of frequency modulation, as well as the rate in which jitter ramps from one random value to the next. Panning between instances of SynthEngine is evenly distributed.
“Turn it up!” – Abe Simpson
The name DeepSynth is a homage to Dr. James A. Moorer‘s piece Deep Note, also known as the infamous THX Logo Theme. Very early in the design, it became evident that DeepSynth is capable of making very Deep Note like drones. This is due to the fact that it does utilize some of the defining techniques used in Dr. Moorer’s piece.
I highly recommend reading Recreating the THX Deep Note by Batuhan Bozkurt at EarSlap. The author conveniently walks readers through each step of the process, providing both audio and Supercollider code examples. If you have ever yearned to create that amazing sound for yourself, here’s your opportunity.