Beck performs at another charity gig in LA, this one for Better Together.
The other names on the bill include Dave Grohl, Santigold, and Greg Kurstin. It seems like they're all using the same house band: Grohl, Justin Meldal-Johnsen, Jason Falkner. Singing back-up include Wendy & Lisa, Susannah Melvoin, and Maya Rudolph (so expect some Prince jams, I guess?).
The rehearsal clip that Susannah Melvoin posted was all of them figuring out "The New Pollution."