This screen is a "juke box"
that allows to hear to all the soundtracks of the demo + some bonus tracks
with quite good sound quality (the soundtracks are played at 25khz oversampled
at 50khz). The musik routine takes more than 50% of the cpu time.
It features two 48x48 shade bobs on 4 planes displayed with the blitter in an
optimised number of passes. The sprites rotation is precomputed.
