is there a way I can take a sound and multiply the waveform by another sounds waveform using the mult command?
The easiest way is to create a stereo track with one sound in the left channel and the other sound in the right channel.
To join two mono tracks to create one stereo track, see: http://manual.audacityteam.org/man/splitting_and_joining_stereo_tracks.html
You can then multiply the sound in the left channel with the sound in the right channel, and return the result to both channels:
(mult (aref *track* 0)(aref *track* 1))
That will amplitude modulate one channel with the other, the result probably won’t be pleasant/musical …
Hey.
I just started to use audacity and I would like to multiply a soundtrack by its self.
so what I did so far was duplicating the sound (named one sound1 and the other sound2)
And put that in Nyquist Prompt:
(mult sound1 sound2)
what did I do wrong and should I use it as a stereo sound?
I am sorry I have no glance about anything 
Thanks for your help!
In the Nyquist Prompt, you can do this (assuming a mono track):
(mult *track* *track*)
TRACK is a special symbol that passes the selected audio to Nyquist. If the selection is a mono track, then TRACK is a sound. If a stereo track is selected, then TRACK is an array of sounds, with the left channel as the first element of the array, and the right channel as the second element.
For more information, see: Missing features - Audacity Support