The Mothers released a series of critically acclaimed albums, including Absolutely Free, We're Only in It for the Money, and Uncle Meat, before being disbanded by Zappa in 1969.

Later replacing Simmons with another ex-Turtle, bassist Jim Pons, this second incarnation of the Mothers endured through December 1971, when Zappa was seriously injured and almost killed by an audience member during a concert appearance in London.

The final non-archival album using the Mothers (of Invention) name, Bongo Fury (1975), featured Captain Beefheart, as well as guitarist Denny Walley and drummer Terry Bozzio, both of whom continued to play for Zappa on subsequent non-Mothers releases.

[9] The group increased their bookings after beginning an association with manager Herb Cohen, while they gradually gained attention on the burgeoning Los Angeles underground music scene.

[10] In early 1966, they were spotted by leading record producer, Tom Wilson, when playing Zappa's "Trouble Every Day", a song about the Watts Riots.

Verve insisted that the band officially rename themselves because "Mother" in slang terminology was short for "motherfucker"—a term that apart from its profanity, in a jazz context connotes a very skilled musical instrumentalist.

It mixed R&B, doo-wop, musique concrète,[15] and experimental sound collages that captured the "freak" subculture of Los Angeles at that time.

[16] Although he was dissatisfied with the final product—in a late 1960s radio interview (included in the posthumous MOFO Project/Object compilation) Zappa recounted that the side-long closing track "Return of the Son of Monster Magnet" was intended to be the basic track for a much more complex work which Verve did not allow him to complete—Freak Out immediately established Zappa as a radical new voice in rock music, providing an antidote to the "relentless consumer culture of America".

[20] Wilson nominally produced the Mothers' second album Absolutely Free (1967), which was recorded in November 1966, and later mixed in New York, although by this time Zappa was in de facto control of most facets of the production.

[21] Examples are "Plastic People" and "Brown Shoes Don't Make It", which contained lyrics critical of the hypocrisy and conformity of American society, but also of the counterculture of the 1960s.

[27] Situated in New York, and only interrupted by the band's first European tour, the Mothers of Invention recorded the album widely regarded as the peak of the group's late 1960s work, We're Only in It for the Money (released 1968).

We're Only in It for the Money featured some of the most creative audio editing and production yet heard in pop music, and the songs ruthlessly satirized the hippie and flower power phenomena.

[29][30] The cover photo parodied that of the Beatles' Sgt Pepper's Lonely Hearts Club Band,[31] its art provided by Cal Schenkel whom Zappa had met in New York.

[33] Zappa has noted that the album was conceived in the way Stravinsky's compositions were in his neo-classical period: "If he could take the forms and clichés of the classical era and pervert them, why not do the same ... to doo-wop in the fifties?

The album and a single consisting of the songs "Deseri" and "Jelly Roll Gum Drop" were released under the alias Ruben and the Jets.

It included British drummer Aynsley Dunbar, jazz keyboardist George Duke, Ian Underwood, Jeff Simmons (bass, rhythm guitar), and three members of the Turtles: bass player Jim Pons, and singers Mark Volman and Howard Kaylan, who, due to persistent legal and contractual problems, adopted the stage name "The Phlorescent Leech and Eddie", or "Flo & Eddie".

[53] Immortalized in Deep Purple's song "Smoke on the Water", the event and immediate aftermath can be heard on the bootleg album Swiss Cheese/Fire, released legally as part of Zappa's Beat the Boots II compilation.

The band thought Zappa had been killed—he had suffered serious fractures, head trauma and injuries to his back, leg, and neck, as well as a crushed larynx, which ultimately caused his voice to drop a third after healing.

Zappa noted that one leg healed "shorter than the other" (a reference later found in the lyrics of songs "Zomby Woof" and "Dancin' Fool"), resulting in chronic back pain.

After releasing a solo jazz-oriented album Waka/Jawaka, and following it up with a Mothers album, The Grand Wazoo, with large bands, Zappa formed and toured with smaller groups that variously included Ian Underwood (reeds, keyboards), Ruth Underwood (vibes, marimba), Sal Marquez (trumpet, vocals), Napoleon Murphy Brock (sax, flute and vocals), Bruce Fowler (trombone), Tom Fowler (bass), Chester Thompson (drums), Ralph Humphrey[54] (drums), George Duke (keyboards, vocals), and Jean-Luc Ponty (violin).

[56] Other albums from the period are Over-Nite Sensation (1973), which contained several future concert favorites, such as "Dinah-Moe Humm" and "Montana", and the albums Roxy & Elsewhere (1974) and One Size Fits All (1975) which feature ever-changing versions of a band still called the Mothers, and are notable for the tight renditions of highly difficult jazz fusion songs in such pieces as "Inca Roads", "Echidna's Arf (Of You)" and "Be-Bop Tango (Of the Old Jazzmen's Church)".

[57] Zappa released Bongo Fury in 1975, which featured live recordings from a tour that same year which had reunited him with Captain Beefheart for a brief period.