Ursula K. Le Guin writes that after having read a good novel, “we may find that we have been changed a little, as if by having met a new face, crossed a street we never crossed before. But it’s very hard to say just what we learned, how we were changed.” The same can be said for having heard Hub New Music’s sampler of NEC faculty member Kati Agócs’s evocative works at Jordan Hall on Sunday night. The concert was one of firsts: the first evening solely dedicated to Agócs’s chamber music; Hub New Music’s first appearance at Jordan. (The group, which formed at NEC in 2013, debuted in a classroom.) Notes on the page and young musicians onstage meshed, enfolding innumerable stories and images into the sounds.