Faust Things

This repository contains various audio related projects programmed in Faust.

Granola

Granola is a monophonic granular live feed processor.

The grain processor is inspired by the Mutable Instruments Beads. The grain window shape control is inspired by the GR-1 Granular synthesizer from Tasty Chips Electronics.

Specifications

• Audio I/O
  • Manual input and output gain control.
  • Recording time: BUFFER_DURATION.
  • The FREEZE button freezes the content of the recording table.
  • Feedback path with attenuation and limiter (with 1 sample delay). The feedback signal comes from the grains output (it's before the dry/wet crossfader).
  • Dry/Wet control.
  • TODO: Stereo I/O with automatic level detection with a limiter.
  • TODO: Gate signal in sync with the grains.
  • TODO: Antialiased output.
  • TODO: Spatialized output.
• Grains generation modes
  • The SEED button triggers a grain.
  • Automatically trigger grains at a periodic rate with the DENSITY parameter (at maximum density there are 1000 grains generated per second (M.I. Beads has a maximum rate of ~260 grains per second).
    Note: The actual number of triggered grains cannot exceed the CONCURRENT_GRAINS value (30 for M.I. Beads).
  • TODO: Automatically trigger grains at a randomized rate.
  • TODO: Start a chain of delayed and pitched grains instead of a single one.
• Grain parameters
  • TIME: Controls the playback position of each grain within the table. In other words, it delays the grains.
  • SIZE: Grain duration from 0.03 seconds to the table length, forward or backward playback.
  • SHAPE: The shape of the grain envelope. The shape control allows to morph the shape from a square (in this case the grain original amplitude is maintained), to an inverted saw (slow release), to a triangle (attack and release time are the same), and finally to a saw (slow attack).
    
  • PITCH: The pitch of the grain (-2..+2 octaves).
    Note: The four grain parameters are latched when a grain is triggered. Hence, the grain parameters remain the same throughout the grain playback but they may differ for multiple grains.
  • TODO: TIME slew limiter for tape like scrubing effect.

Usage

_ : Granola(BUFFER_DURATION, CONCURRENT_GRAINS).ui(uix) : _

Where:

• BUFFER_DURATION: buffer duration in seconds.
• CONCURRENT_GRAINS: (int) number of grains allocated.
• uix: (int) the UI instance number.

A demo function of Granola with a limiter, a LPF and a reverb on the output.

_ : Granola(BUFFER_DURATION, CONCURRENT_GRAINS).demo : _, _

Examples

// A Granola's demonstration setup with a 5 seconds buffer and an up-to-15-grains polyphony.
process = Granola(5, 15).demo;

// A Granola grain processor.
// It has a 1 second audio buffer and up to 30 grains playing a the same time.
process = Granola(1, 30).ui(0);

// Two Granola instances allowing to process each channel of a stereo signal differently.
// They have a 5 seconds audio buffer and up to 15 grains playing a the same time.
process = Granola(5, 15).ui(0), Granola(5, 15).ui(1);

// Two Granola instances sharing the same user interface making a stereo grain processor.
// They have a 5 seconds audio buffer and up to 15 grains playing a the same time.
process = Granola(5, 15).ui(0), Granola(5, 15).ui(0);

// As the Granola grain processor is able to play many copies of the input signal simultaneously,
// it may rapidly saturate its output. This could be avoided by manualy reducing the output gain,
// by selecting a smoother grain-window shape and/or by placing a limiter in the circuit path.
// Also note that Granola pairs well with a reverb.
process = Granola(2, 30).ui(0) : co.limiter_1176_R4_mono <: dm.zita_light;

// Granola used as a delay like effect. Parameters are taylored for the default audio file
// of the Faust web IDE (wait 5 seconds to let the table be filled). Play it looped.
process = Granola(5, 10).grains(0, _, 4.76, 0, 0.5, 0, 0.5, 0.5, 0.03, 0.5, 1, 0, 0, 0.5);

// Granola used as a complex feedback effect: the most important parameter here is the 6th,
// the feedback control. Feed the input with some audio (the looped  default audio file, for
// example). Let the feedback grow. It will gradually decrease when the sound is muted.
//
// __Be careful with your ears, this can get very loud.__
//
process = Granola(5, 10).grains(0, _, 4.72, 0, 1, 0.4, 1, 0.6, 0.604, 3, 0.972, 0, 0, 0.5);