The upper track will become the left channel of the new stereo pair, and the lower the right channel.

Make Stereo Track Use this command on the upper of two adjacent, single channel tracks which you want to join into one stereo track.

Currently Audacity does not support multi-channel playback. 'Mono' feeds the output of that track to both left and right speakers on most two channel systems 'Left Channel' and 'Right Channel' feed it only to that respective speaker.

Mono, Left Channel and Right Channel Mainly used on multiple single channel files (ones that are not the split left and right channels of a stereo pair) so as to mix to a final stereo track.

As it's so short, we can zoom in to show the closer spacing of the cycles as the frequency (and hence the pitch) increases from left to right. This image is a waveform view of an extremely short chirp, one tenth of a second, with only a few cycles, where the pitch increases very rapidly. The second half of the waveform is the word 'Audacity' spoken by a male voice.

Zooming would show the individual cycles in the waveform (the positive and negative peaks) occurring much closer together at the end of the sound.

What you can't see without zooming much further in is that the pitch of this tone is gradually increasing.

The horizontal line centered on 0.0 is silence. The linear scale on the left goes from +1 at the top (the maximum possible loudness without distortion when the signal is positive) to -1 at the bottom (the maximum when it is negative). This first half of this waveform is a 'Chirp' tone which stays at the same amplitude (loudness), as shown by the horizontal top and bottom.

Audacity spectrogram