Hot Rats is the second solo album by Frank Zappa. It was released in October 1969. The album consists of six tracks, five of which are instrumental (the song "Willie the Pimp" features a short vocal by Captain Beefheart). It was Zappa's first recording project after the dissolution of the original Mothers of Invention. In his original sleeve notes Zappa described the album as "a movie for your ears."
Because Hot Rats focuses on long instrumental jazz-like compositions with extensive soloing, the music sounds very different than earlier Zappa albums which featured short songs with satirical vocal performances with extensive use of musique concrete and editing techniques. The only member of the Mothers to appear on the album is multi-instrumentalist Ian Underwood who was also the primary musical collaborator. Other featured instrumentalists were noted guitarist-songwriter Shuggie Otis (the son of renowned R&B musician and broadcaster Johnny Otis) on bass, drummers Aynsley Dunbar and John Guerin and violinists Don "Sugarcane" Harris and Jean-Luc Ponty.
This was the first Frank Zappa album recorded on 16-track equipment and one of the first 16-track rock recordings released to the public. Recording machines with 16 individual tracks allow for much more flexibility in multi-tracking and overdubbing than the 4 and 8-track tape recorders that were standard in 1969. While Zappa was recording Hot Rats in Los Angeles, The Beatles were working on their Abbey Road album at EMI's soon to be famous Abbey Road Studios in London. By comparison, The Beatles were limited to 8-track technology. Hot Rats still stands out as one of Zappa's greatest musical and technological achievements and remains one of his most popular albums.