# Instrument X, Phase Modulator Described by John M. Chowning in his 1977 paper, "The Synthesis of Complex Audio Spectra by Means of Frequency Modulation," shows how to create harmonic-rich waveforms mostly out of sine waves. It was the primary sound source of the Yamaha DX7. It also happens to be a great way to create bass and percussion sounds, among other things. > [!cite] Lore > ![[10-the-eruptor.png]] > The Eruptor (art by Dead Carcosa) ## Phase Modulator From [[Signal Music, Atmosphere]]. This generates phase-modulated notes where the note, modulation depth, ratio, feedback, and amplitude are all modulated with evolving sources of randomness. I used `[gen~]` to model a phase-modulating oscillator. It is like a two-operator phase-modulating synth. > [!example] > ![[image-107.png]] > The basic patch [!example] > ![[image-108.png]] > The `[gen~]` patch within the main patch