Set the Sync mode for the Playback plug-in

When you add an audio file to the Playback plug-in, MainStage looks for tempo information in the file. For audio files containing tempo information (including Apple Loops and files exported from Logic Pro), the file is scanned for transients (short bursts of audio energy that usually occur on rhythmic beats). Transient information is stored in the audio file and used to play the file with the best audio quality, even when the file is played at a different tempo or pitch. For these audio files, you can use the Sync feature to set whether the audio file plays at its recorded tempo or uses the current tempo of the concert. When Sync is set to Off, the audio file plays at its recorded tempo, regardless of the current tempo of the concert. This can be desirable, for example, when the audio file contains non-pitched sounds or a sound effect. When Sync is set to On, the audio file plays at the current tempo (set by the patch, set, or concert, by tapping the tempo, or by listening to MIDI beat clock). This makes it easy to keep backing tracks, for example, in time with each other and with your performance. Setting Sync to On can affect audio quality.

You set the Sync mode for an instance of the Playback plug-in from the Sync pop-up menu, located in the lower-left corner of the plug-in window.