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



Is there

  1.  A way to make the amplitude rise and fall over time?
  2.  Vary the duty cycle over time, from say 300Hz to 600Hz and back down to 300Hz then repeat?



Any advice welcomed.

Thanks in advance.

Darryl