Produced by songwriters Jerry Leiber and Mike Stoller, Procol's Ninth featured a slightly different direction from the previous album, with a much starker sound than Chris Thomas's more elaborate productions.

According to an interview with guitarist Mick Grabham, conducted by Roland Clare for the 2009 reissue, Leiber and Stoller focused less on the production sound and more on "the structure of the songs".

[3] Procol's Ninth was the first release from the band to feature non-original songs: a remake of The Beatles' "Eight Days a Week" and Leiber & Stoller's own "I Keep Forgetting".

"[4] As included on Ninth, it differed substantially from the more psychedelic unfinished version of the song that was ultimately released as a bonus track on the 2009 reissue of the band's first album.

Salvo reissued the Procol Harum discography in 2009; the albums were remastered by Nick Robbins, with bonus tracks selected by Gary Brooker and Keith Reid.