Select the Type of Apple Loops to create by clicking one of the two radio buttons:
Loop: These Apple Loops conform to project tempo, scale, and key. In order to ensure that the loops conform properly, the region lengths must match a whole number of beats. Choose Loop for loops of musical material.
One-shot: These Apple Loops ignore tempo, scale, and key information, and have a fixed duration. Choose One-shot when creating Apple Loops of sound effects, dialog, and other sounds that are not necessarily musical in nature.
Note: If your region lengths do not fall exactly on a PDF
Control Surfaces Support Guide: PDF