Apple Soundtrack Pro 2 - Manual (Page 175)

Chapter 5 Working in the Timeline 175
A Timeslice selection rectangle appears over the portion of the clip and the File Editor
tab displays the same selection in its waveform view. By default, the selection includes
all of the clip’s envelopes.
To adjust the size of a Timeslice selection, do one of the following:
m Drag any of the four edges of the selection to extend or shorten that side of the
selection rectangle.
m Shift-click any track you want to include in the Timeslice at the opposite end of the
area you want to select.
Timeslice selection
File Editor selection