Logic Pro 9 User Manual - Help Library - Apple

Snapping Edits to Zero Crossings
If Edit > Snap Edits to Zero Crossings is turned on, adjustments to the start or end position
of a region are snapped to the nearest point where the waveform crosses the zero axis.
Put another way, there are certain crossover points in a sample (a drum loop, for example)
that are closely matched in level to other points in a sample. If two closely matched points
are used for the start and end points of the sample, the loop plays back without noticeable
glitches in the audio.
When adjusting the start point, the area preceding the selected point is scanned for a
smooth crossover point. When adjusting the end point, the area that follows the region
is scanned for a smooth crossover point.
To snap audio edits to zero crossings
1 Click the title bar of either the Audio Bin or Sample Editor to give the window key focus.
2 Choose Edit > Snap Edits to Zero Crossings (or use the corresponding key command).
Note: The Snap Edits to Zero Crossings option can be set independently for the Sample
Editor and Audio Bin.
Moving a Region Within an Audio File
You can also move an entire region within an audio file in the Audio Bin window.
To move the region area within the audio file
1 Position the pointer over the center of a region.
2 When the pointer turns into a two-headed arrow, drag the region to the left or right.
Two-headed arrow cursor
Note: If you want to adjust the boundaries of the region without moving the anchor,
hold down the Option key during the operation. This applies to moving the start or end
point, as well as moving the whole region.
Editing the Audio Region Anchor
The anchor is the temporal reference point of an audio region. When you move an audio
region, it’s not the start point that is displayed in the help tag (as with MIDI regions)—it’s
the anchor point.
Chapter 12 Getting to Know Regions
357