Though this album, along with several others, was released by Frank Zappa's record label without his permission, it still stands as one of his finest achievements. A completely instrumental record upon its initial release and as presented here, Sleep Dirt, later released on CD with several vocal overdubs, shows signs of Miles Davis, Jimi Hendrix, David Gilmour, Robert Fripp, among the potential influences. It is a furious example of progressive rock, with several pieces defying any categorization at all. Most of the tracks were intended for release as part of the 4-LP Lather collection that the record company quashed, but which saw issue after Zappa's death. "Filthy Habits" sets the tone, with a seven-and-a-half minute astral projection that's simply sublime. "Flambay" hits the nightclub for Zappa's idea of jazz. The title track captures Zappa at his more subdued and introspective, which was always a highlight coming from a man so naturally outrageous. "The Ocean Is The Ultimate Solution" is more in tune with Zappa the innovative instrumental scavenger.