Warthur
Zappa's first commercially-focused album after the 1971 album which left him unable to tour for a year inaugurates the mid-1970s phase of the Mothers. Lyrically speaking, the approach picks up where the Flo and Eddie years left off - a mixture of surreal humour and really filthy jokes dominates - but Zappa takes on more of the vocal duties himself, perhaps as a way of getting used to his new, deeper voice (a lasting consequence of his injuries). However, unlike the Flo and Eddie years the comedy songs aren't partitioned off from the jazz-rock numbers: instead, the musical complexity and quality remains firm across the whole of the album, and the large band includes a range of talented instrumentalists (and, for this album only, Tina Turner and the Ikettes on backing vocals) whose soloing skills are showed off across the album.
It's not the absolute best album Zappa would make in this style, but it's a very strong statement of intent indeed, as well as a substantial improvement over the Flo and Eddie years.