This is a bootleg album, released by Frank Zappa without enhancement, and also available as part of the Beat the Boots! box set. It features a live performance by the Mothers of Invention in July 1968 at the Ark, a club in Boston. Apparently, the Mothers themselves were recording the show, so it appears in adequate sound quality, and it catches the Mothers as they were moving from the doo-wop sound of their Verve albums to Uncle Meat. There is an extended version of "King Kong," from the latter.
AllMusic Review by William Ruhlmann