Flea brought his Honora Band to KOKO in London on May 26, and Thom Yorke showed up to make it a night worth talking about, joining the set for performances of “Traffic Light” and a euphoric run through Marvin Gaye’s “Got to Give It Up” that had the crowd dancing and the internet paying attention the next morning. The collaboration draws on a deep and ongoing creative friendship: Flea and Yorke were both part of Atoms for Peace, the supergroup that also included Nigel Godrich and Joey Waronker, who briefly reunited in 2018, and the two later connected on “Daily Battles” for Edward Norton’s film ‘Motherless Brooklyn.’ Watching them share a stage in an intimate London venue, loose and joyful, is a reminder of what happens when genuinely great musicians play for the love of it.