Apple Logic Pro 8 - Manual (Page 658)

658 Chapter 31 Beat Mapping Regions
Beat Mapping With Audio Regions
This works in a similar fashion to that described above for MIDI regions. The main
difference is that Logic Pro must first analyze audio regions in order to find rhythmically
prominent spots, which can subsequently be linked to a bar position. Logic Pro
searches for transients when analyzing audio regions. Transients are positions where
the audio recording becomes a lot louder—over a very short time span (a signal spike,
in other words). This is typical of drum recordings, but the analysis of other instruments
or complete mixes (depending on the musical context), can also produce usable
results.
To detect transients in an audio region:
m Select the desired audio region, and click the Analyze button in the track header of the
Beat Mapping track.
Following analysis, the transients are displayed as small vertical lines at the bottom of
the Beat Mapping track. The remaining steps of the beat mapping procedure are as
described above for MIDI regions.
It is also possible to analyze several selected audio regions at once. An alternative
method for audio region analysis is to drag them directly onto the Beat Mapping track.
Improving Beat Mapping Accuracy
The Detection Sensitivity value field in the track header allows you to retrigger the
analysis procedure if the results are not as expected. A higher Detection Sensitivity
setting will detect more transients, which can be useful if dealing with less distinct
accents in the music (such as soft drums in a loud mix). On the other hand, a higher
Detection Sensitivity setting might lead to the detection, and display, of transients that
have no meaning for the rhythmic structure of a region. In general, you should begin
with a lower Detection Sensitivity setting, and only switch to a higher setting if obvious
rhythmic elements in the music aren’t recognized correctly.
Note: The detection ability is independent of the overall volume of an audio region. In
other words, the results will be the same if you normalize a region.