Grackle: Unique 3-operator FM Synth Voice

Grackle from Entropic Loop is a three-operator phase modulation voice with a unique take on a familiar architecture. Phase modulation, popularly known as FM synthesis, gained popularity in the 1980s with the rise of more affordable digital synthesizers such as the Yamaha DX-7 after being developed by researcher John Chowning while at Stanford University in the late 1960s. While Grackle uses the fundamental techniques found in FM synthesizers, its implementation is unique; unlocking a new dimension in digital synthesis with sounds that stretch from the familiar to deep uncharted territory. Although it has a distinctly digital sound, Grackle's interface is immediate and playable in a way that almost feels analog.

0:34 intro

1:03 feedback into actualFM, cycling envelope

1:36 interface sections

2:11 raw modulation oscillator output

3:05 intervals

3:39 algorithms

4:39 envelopes

Phase Modulation Synthesis
The principles that underlie the record player give a rough approximation of the relationship between frequency and phase applied to phase modulation. Imagine if you record a sine wave onto what is called a locked groove record, i.e. a record that continuously spins on a loop without moving inward. Locked grooves are typically placed at the end of the side of a record and just contain silence. However, they are sometimes used to create infinite loops, and in our hypothetical example, a single sine wave.

The speed that the record player spins determines the pitch of the sound, if it spins faster, then the sound is higher, if it spins slower, then the sound is lower. The position of the stylus on the vinyl record is the phase of the sine wave in this example. If you rapidly change the position of the record in relation to the stylus such as scratching the record, the pure sine wave tone changes in character.

Phase modulation synthesis uses one or more sine wave oscillators to change the phase of another sine wave oscillator (the modulation sine wave oscillators in this example are our turntablists). This transforms the simple sine wave into a more complex waveform with more harmonics, but retains the fundamental pitch of the original sine wave (since it is still rotating at the same speed.

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