Introduction to MIDI and Computer Music: Soundbite Tempo Conformance

Digital Performer Soundbite Tempo Conformance

Say you have several soundbites that contain pulsed musical material, and you want them to play together. If they pulse at different rates — that is, they have different tempos — then you've got a problem. You will have to time-scale some of the soundbites to synchronize their tempos. Also, you'll want the measures and beats in the Digital Performer time ruler to align with the beats you hear in the soundbites.

Here's how to handle this situation.

Before making soundbites, trim your sound files in a sound editor so that they play for an integral number of beats. For a typical drum pattern that you intend to loop, this means you should have the file start exactly on the first beat of the pattern and have it end just before the first beat of the next iteration of the pattern. For advice on using the DSP-Quattro editor for this purpose, see Assignment 3, Part 4.
Don't try to use a large amount of audio (like 20 beats or more). It's possible that the tempo within the file will drift over this amount of time, and this will mess up the synchronization between soundbites.
It pays to be careful at this stage, because your success at manipulating the soundbite tempos in Digital Performer depends on having cleanly trimmed sound files.
Import the sound files into Digital Performer, and place the resulting soundbites on tracks.
Open the Sequence Editor so you can see the soundbites more clearly.
For each soundbite, select the soundbite and give the Audio -> Set Soundbite Tempo command. In the right-most edit field, type in the number of beats you think the soundbite contains. For example, if you think the soundbite spans exactly 4 beats, enter 4|000. (Ignore the other edit fields.) Press OK.
Select the soundbite whose tempo you want the sequence to have. This will be the soundbite that you do not want to time-scale.
Give the Audio -> Adjust Sequence to Soundbite Tempo command. This will just make the sequence have the same tempo as the soundbite. The soundbite will not change in any way. If you've placed the soundbite at the beginning of a track, you should be able to tell that the beats in the soundbite align with the time ruler.
Select a soundbite that has a different tempo from the one you just used. Give the Audio -> Adjust Soundbite to Sequence Tempo command. This will time-scale the soundbite so that it fits the tempo of the sequence. This means it will align with other soundbites that have that tempo.
You may find that the synchronization is not perfect. This is either because the tempo of the soundbite drifts or because you weren't able to trim it to an exact number of beats (which is often very hard).