Thank you Thomas, I think you've answered my questions. On 25/2/21, 8:11 am, "Dr. Thomas Tensi" <t.tensi@xxxxxx> wrote: Hello Darryl, you wrote: > I’m trying to simulate a square wave signal. So far I have this, > which should be a 400Hz square wave. > play -V -r48000 -n synth square 400 0 0 This looks quite realistic to me. > Is there > 1. A way to make the amplitude rise and fall over time? This is easy: you can either use another synth modulation or a tremolo: play -r48000 -n synth square 400 0 0 synth sine amod 0.5 or play -r48000 -n synth square 400 0 0 tremolo 0.5 50 where tremolo also allows to set the modulation depth via its second parameter. > 2. Vary the duty cycle over time, from say 300Hz to 600Hz and back down > to 300Hz then repeat? I am not sure whether you mean a pulse width modulation or a frequency modulation (the latter sounds like a frequency modulation...)? In principle some sort of frequency modulation is possible via fmod instead of amod above, but it is a double-sideband suppressed-carrier amplitude modulation and not a real frequency modulation as you request. I do not know of a genuine frequency modulation in real-time. But when real-time is not required, you could define a sweep parameter for the synth like e.g. sox -r 48000 -n part1.wav synth 5 square 300-600 sox -r 48000 -n part2.wav synth 5 square 600-300 play part1.wav part2.wav The kind of sweep can be specified by giving either '+' '-' '/' or ':' as the separator between frequencies. Hope this helps! Best regards, Thomas _______________________________________________ Sox-users mailing list Sox-users@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/sox-users _______________________________________________ Sox-users mailing list Sox-users@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/sox-users