I’m on Firefox v28.0 & notice a similar effect to the one in the picture posted by the person above.
One suggestion I’ll make is to use youtubetime.com to start all videos right when the song begins, unless you really want all the talking beforehand included. For example, use this link and the video will begin right as the musicians take a breath before they play: http://www.youtube.com/watch?v=fZ8bzWWo_G4&t=1m17s
Also several video links must be wrong because they lead to videos that don’t exist, displaying YouTube’s “not there” sort of warning.
I’m personally not a huge fan of the every-page-in-one-long-page style but if that’s what your client wants then you’re design here is quite nice.