Make in or out of step

You can alter the trip time for the path, just by making the path longer.

change the path

Vary the paths to make the trip times either different or the same. If they’re different, then the vibrations will be out of step. If the trip times are the same, then the vibrations will be in step.

ahead or behind

Here you can make two vibrations more or less in or out of step. One of the vibrations is ahead, the other lags behind.