External Combustion – the second album and first as band leader of the Dirty Knobs – is proof that lightning can strike twice. His first record, Wreckless Abandon, was released in November 2020 to a great reception, gaining attention from Broken Record, Vulture, WTF with Marc Maron podcast, LA Times, Rolling Stone, American Songwriter, Billboard and many more. The Dirty Knobs made External Combustion in three weeks over the summer of 2021, and "The band became this spontaneous type of combustion”, Campbell recalled, recounting how the band became more intuitive the longer they played. Campbell claims he was never offered a solo deal in his four decades with Tom Petty and the Heartbreakers, despite also writing and producing for artists like Roy Orbison and Don Henley. "I wouldn't have known what to do with it," he adds quickly. "I was Tom's partner. Lyrics and singing – he could always do it much better. But I was writing and recording more music than Tom could deal with. That's when I got the Dirty Knobs, which gave me a chance to try singing. So I started woodshedding. And then when my life changed (with Petty's death in October 2017) it was, 'Time to do this now.'"
X-Legged Sally (XLS) is a Belgian avant-garde rock/jazz-band founded in 1988 by composer Peter Vermeersch, and disbanded in 1997. They were one of the first bands from Belgium to combine a set of very different musical styles (jazz, rock, improvisation and classical), becoming a starting point for the Belgian indie music scene that developed in the nineties. Initially, X-Legged Sally was formed to compose and perform the music Peter Vermeersch wrote for dance productions, such as Immer das Selbe Gelogen (Always the Same Lies), released as a live cd in 1991. Vermeersch' composing style was becoming too demanding for the constraints of sheet music such as was used in his earlier band Maximalist! From the beginning, improvisation played an important role in XLS' songs. The first X-Legged Sally concert took place in November 1988. Soon, XLS became a band in its own right, although there would be cooperations with dance ensembles throughout the existence of the group.