Synthesis

synth — generating audio from nothing

-n in the input position means “no input file; generate audio.” synth tells sox what to generate.

play -n synth duration waveform frequency

Waveforms

play -n synth 3 sine     440
play -n synth 3 square   440
play -n synth 3 triangle 440
play -n synth 3 sawtooth 440

Noise

play -n synth 5 whitenoise
play -n synth 5 pinknoise
play -n synth 5 brownnoise

Sweeps

Specify frequency as a range to sweep:

play -n synth 5 sine 100:8000    # 100 Hz → 8 kHz over 5s

Chords

Multiple waveforms on one synth generate simultaneously:

# C major: C4, E4, G4
play -n synth 2 sine 261.63 sine 329.63 sine 392.00 gain -6

The output format follows your system’s default audio configuration, which may not be what you want. Specify it explicitly with output format flags between -n and the output filename (see “Fully-specified output” in chapter 5):

sox -n -r 44100 -b 16 -c 1 out.wav synth 3 sine 440

Adding effects

play -n synth accepts a full effects chain:

play -n synth 10 sine 440 reverb 80

Taming sox