Recording for slow motion in post

[Guest]

I am shooting a music video this week. I want to record the artist singing the song 50% faster than it's usual tempo so that when I go to post and slow down the footage, everything will be moving in slow motion but with his lips singing in cue (You know what I mean right? They do this alot in film where they record in 48fps, and playback in 24. It's a cool effect) However, when I slow down the footage to match the original beat, the sync strays off after a few seconds. Is there a trick or technique to do this properly?

thanks

Anthony

[PrestonH]

What are you using for audio playback on the set for lip sync?