Early in the process, Saltzman, along with the three mentors, matched the singers with commissioned composers, building on the recital programs that were taking shape. Riley’s recital is bookended by two new pieces from L.A. composer Nicolas Lell Benavides (Oct. 2). Birchell debuts a song cycle by Michael Welsh (Oct. 10). And on the program for Metzler: a premiere from pianists Sarah Gibson and Thomas Kotcheff (Oct. 16). That’s in addition to music by Samuel Barber, Alexander Zemlinsky, William Grant Still, Jake Heggie, and more.