"Breathe42" is a DJ Nerd42 mashup of Mars ILL's "Breathe Slow" (Backbreakenomics, 2003) with Pink Floyd's "Breathe". (Dark Side of the Moon, 1973) Adam Thorton is playing bass guitar. It was released on January 2, 2009.
All mirrors point to the same file, which is in FLAC format. If your media player can't play FLAC, get a better media player or convert to your format of choice because this track is way too awesome for me to encode it at a low bitrate.
 Get the instrumental
I've uploaded the instrumental in response to a request. All mirrors point to the same file, in FLAC format again.