Since 2008, he has served as co-director of the non-profit label New Amsterdam Records along with William Brittelle and Sarah Kirkland Snider.
[6] In 2011, Greenstein curated the Ecstatic Music Festival at Merkin Concert Hall, giving indie-classical and indie-pop artists like Owen Pallett, Shara Nova, Julianna Barwick, and Victoire an "uptown" arena to showcase their sophisticated endeavors.
[8] Critics have frequently commented on Greenstein's idiosyncratic style, which maintains a pulse-driven poppish sensibility while employing a sophisticated harmonic language.
[9] He is often identified with a group of young New York-based composers like Nico Muhly, Missy Mazzoli, and Corey Dargel, who fuse the accessibility of minimalist classical music with popular vernaculars to create genre-indifferent works, commonly labeled "indie-classical".
[9][10] In a detailed analysis, musicologist Kyle Gann remarked on Greenstein's typically polymetric compositional structures, giving his music a "foot-tapping pop surface in front of a background rhythmic complexity", akin to the 1980s advent of totalism.