Apple Logic Pro 9 - Manual (Page 601)

Using Beat Detection to Create Tempo Changes
You can use beat detection to find the average tempo of one or multiple selected audio
or MIDI regions. The beat detection process detects a maximum of five tempi across the
region(s), providing an indication, from high to low, of the reliability of each estimate.
The most reliable value—at the top of the list—is selected by default. It is possible to
modify this average tempo value using a multiplier, divisor, or decimal rounding. You
also use this algorithm to decide how and where to apply the tempo change.
To adjust the tempo to the average of a region, or regions
1 Select one or more regions in the Arrange area.
2 Choose Options > Tempo > Adjust Tempo using Beat Detection from the main menu bar
(or use the corresponding key command).
601 Chapter 18 Working with Tempo and Audio Regions