Background (Updated October 2021)

Since version 4 Nyquist plug-ins, the global variable that passes the track audio from Audacity to Nyquist changed from S to *TRACK*.

For ;process and ;analyze type plug-ins, audio is passed from audio tracks to Audacity as the value of *TRACK*.

• *TRACK* is a global variable.
• For mono tracks the value of *TRACK* is a sound object.
• For stereo tracks the value of *TRACK* is an array with two elements. Each element is a sound object.

Stereo tracks:
The first element of *TRACK* may be accessed with:
(aref *track* 0) which is the sound from the left channel.
The second element, (aref *track* 1) is the right channel.

To return a stereo track to audacity, an array with two elements, where each element is a sound needs to be returned.
example: