What is the song that plays when Muramasa charges at Ichigo? I heard several times but can't find the song. It plays in season 13 in episode 253, starting around 9:58, right when Muramasa charges at Ichigo after turning into a hollow.
It's Shadow's Masquerade. 

The first usage of the soundtrack is in episode 88 of the Season 4: Bount arc. The music itself is the track #16 from BLEACH Original Soundtrack 2.