Ian Anderson, frontman of Jethro Tull, has named Roy Harper's 1967 album "Come Out Fighting Genghis Smith" as his favourite cult classic record. The revelation, made in a 2021 interview with Classic Rock, underlines the outsized influence Harper had on the prog-rock genre, with Anderson crediting him as a "primary influence" whose complex lyricism and genre-blending shaped Jethro Tull's own musical direction.

Harper, a Mancunian folk musician, was admired by numerous major acts including Led Zeppelin, Pink Floyd and The Who, as well as later artists such as Kate Bush, Fleet Foxes and Joanna Newsom; Pink Floyd even featured him on their track "Have a Cigar" from "Wish You Were Here". Anderson singled out the album's 11-minute track "Circle" for its innovative structure, but said the song "Another Day" was the one that "really resonated" with him personally, recalling how he bought the record shortly after moving to London. The album marked Harper's attempt to break free from conventional folk-rock and is regarded as a significant, if under-recognised, precursor to progressive rock.