Costello presents himself as much as a fan as a participant, and his participation is relentless. He has evolved into one of the most spirited accomplices in tribute gigs, variety evenings, and extracurricular combinations.
This according to “Brilliant mistakes: Elvis Costello’s boundless career” by Nick Paumgarten (The New Yorker LXXXVI/35 [8 November 2010] pp. 48–59.
BONUS: Back in the day.