Let's say that you have a great rhythm guitar performance, but it was recorded without the benefit of a click track, so its tempo may vary between, say, 76 beats per minute (BPM) and 82 BPM. You might think that track is unusable. Not true! With MOTU's Digital Performer, you can match the tempo of a sequence to that of an audio track using DP's Beat Detection Engine and Adjust Beats feature! Here's how:

Drag your guitar part into a new DP track, lining it up with bar 1 of your sequence. DP's Adjust Beats feature lets you use the peaks in your audio track waveform as a guideline for lining up bar lines (by dragging them on the time ruler), but adjusting one beat at a time can be time-consuming, so here's where the Beat Detection Engine comes into play: It looks at the peaks in the waveform and attempts to determine the beat and tempo information from this. If your audio waveform has dynamic peaks that can be interpreted as beats, you may be all set. Next, select your guitar track and then choose Audio > Adjust Sequence to Sound Bite Tempo. That adjusts the Conductor Track to match the tempo map created by the Beat Detection feature. The next step is to set Tempo Control to Conductor Track. Make sure that in your Adjust Beats window you select "Apply adjusted beat's tempo until end of sequence" and also "Preserve realtime performance."