Apple Soundtrack Pro 2 - Manual (Page 203)

Chapter 6 Editing Audio Files 203
2 Drag the pointer to select the part of the left channel you want to work with.
As you drag, the right (lower) channel of the audio file becomes darker in the waveform
display. You can also double-click in the upper part of the waveform display to select
the entire left channel.
To select the right channel of an audio file:
1 Move the pointer near the lower edge of the waveform display.
The pointer changes to the letter “R.”
2 Drag the pointer to select the part of the right channel with which you want to work.
As you drag, the left (upper) channel of the audio file becomes darker in the waveform
display. You can also double-click in the lower part of the waveform display to select
the entire right channel.
Left channel selected
Right channel
selected