I shot two music concerts with my A1 and recorded sound to a separate recorder. The music was sweetened in Pro Tools and then exported as 16bit 48K aiff files and laid back to FCP. Concert 1 was recorded at 1080/24F and the edited audio stays in sync for the entire concert (1 hour). Concert 2 was shot in 1080/60 and the 16bit, 48k aiff file drifts out of sync after a couple of minutes.

Can anyone explain what's going on and what should I do to sync the audio for concert 2?

Thank you,
Bruce

Well, of course, the camera clocked differently in the second concert's mode. But if everything was shot continuously, then one shrink or one stretch to make the audio the same overall length as the video should bring it all into synch.