as much to my knowledge that I can give you, yes, you have the right idea. Shoot your footage of the singer lip syncing to a recording of the music played through a sound system/boom box, whatever you want to use, you would then utilize the original music recording in your editing software and sync the video to the audio of the music using the ambient sound recorded at the shoot or visually with the video. you could then insert various shots to cover any sync problems. Good luck and happy editing.
John
