On the first layer with the track that has audio, you would set the play mode to Play forward audio (or similar) and set that to sync ID 1. On the second layer, you would set the play mode to sync ID 1. The clips will then play identically. Basically frame 1 of layer one will trigger frame 1 of layer 2. So make sure they are the same length. Each layer is still its own file and they can be positioned differently and routed to different mixes etc..

Ryan.