Synthesizing Changing Square Wave In Nyquist

I have this tone I am trying to synthesize in Nyquist.
It is a square wave with some sort of modulation.

Here is an oscilloscope view of the signal:
test.gif

Use OSC-PULSE https://www.cs.cmu.edu/~rbd/doc/nyquist/part8.html#index393

Steve, osc-pulse can only do pwm. The audio is not pwm, it is some other type of modulation.