Conversation so far:
How did Bagdasarian go about getting the voices of the chipmunks?
He sped up the playback to create high-pitched voices.
Did Bagdasarian use different people for each of the chipmunks?
The voices of the group were all performed by Bagdasarian,
How did Bagdasarian come up with the voices for each chipmunk?
He sped up the playback to create high-pitched voices.

Question: Did he do this technique with any other characters he came up with?
Self-contained rewrite: Did Bagdasarian do the high pitch voice technique with any other characters he came up with besides the chipmunks?