Timeline Audio Track not playing audio?

I've got a timeline track, with an audio source assigned and a clip in the track. The audio source also has a proper output mixer channel and all. However when I play the timeline the audio is not played.

Note that if I put a clip into the source and just have it play OnAwake it plays properly so it can't be the audio source settings or a missing audio listener or something. It's just when audio should be played through the track (also not in preview mode but in proper play mode) nothing happens.

anyone got any ideas?