One of the great guitarists of the classic rock era, Mike Campbell served as Tom Petty's lieutenant, sticking with him through solo records and with the Heartbreakers. Campbell occasionally worked apart from Petty -- notably, he gave Don Henley the music for his 1984 hit "The Boys of Summer" -- but he was there even when Petty went solo or when he reunited Mudcrutch, the country-rock group the pair played in prior to the Heartbreakers. The guitarist also launched a band called the Dirty Knobs during some downtime with the Heartbreakers around 2000, and after Petty's unexpected death in 2017, he made that band his primary concern, releasing their debut, Wreckless Abandon, in 2020. Campbell moved his name above the Dirty Knobs in the billing for their second album, External Combustion, but the group continued to play rock & roll in the vein of the latter-day Heartbreakers.