Keyboardist Don Airey played bass on Painkiller
because Judas Priest bassist Ian Hill was unable to take part in recording sessions due to illness. Airey, who had worked with both Ozzy Osbourne and Rainbow before becoming Deep Purple's keyboardist in 2002, played most of the album's bass parts on a Minimoog. Speaking with AntiHero magazine
in 2020, he recalled:
"All the bass parts are me playing on the mini. It's Moog bass on the whole album, that was Ian Hill's bass mixed in as well on parts. But at the time Ian wasn't very well. So, he wasn't at the sessions. So, I got made to do all the bass and they kept it."