On Sept. 19, star countertenor David Daniels and the Academy of St. Martin-in-the Fields take the London stage to perform re-imaginings of Handel works by Michael Nyman, Nico Muhly, John Tavener, Craig Armstrong and Jocelyn Pook. Says Muhly of his contribution, “What I always want is for [the original Handel aria] to last for ever. To live in the music. So that’s what I did.”