This was a one-day mini-festival in the park in London (though there were also separate lineups in the following days in the same location). The Strokes headlined Beck's day, and he is the second act.
I guess Beck was supposed to play a song with The Strokes, but at the last minute had to pull out and did not.
[people and bands
Bass: Justin Meldal-Johnsen
Drums: Joey Waronker
Guitar (Acoustic): Beck Hansen, Jason Falkner
Guitar (Electric): Beck Hansen, Jason Falkner
Harmonica: Beck Hansen
Headliner: The Strokes
keyboards: Roger Joseph Manning Jr.
Other Band: Future Islands, Syd Arthur
Piano: Roger Joseph Manning Jr.
Synthesizer: Jason Falkner, Justin Meldal-Johnsen, Roger Joseph Manning Jr.
Vocals: Beck Hansen
Vocals (Background): Jason Falkner, Justin Meldal-Johnsen, Roger Joseph Manning Jr.