The length of imported audio regions and the project tempo are directly linked. If you change the tempo at a particular project position, the length of regions at, and after, this position changes. You won’t hear a difference in the playback speed of the imported audio, but all MIDI or software instrument regions will be out-of-sync with all audio regions. Audio regions that are lengthened (by increasing the tempo) may overlap with other regions on the same track, resulting in the earlier region being played in full at the expense of the beginning of the following region. All audio region loop lengths (set with the Inspector Loop parameter) change, resulting in irregular loops and strange polyrhythms between tracks. Fortunately, you can circumvent these problems with Logic Pro.