Mark So (born June 14, 1978, in Syracuse, NY) is an American experimental composer and performer living in Los Angeles.

His works, numbering over 800 (including a group of about 300 concerning poems of John Ashbery), are mostly text-based and influenced by New York School aesthetics, Fluxus, and the Wandelweiser composers collective.

So's work has been described as using disparate media to explore ordinary situations in various open frames of perception and action, typically proceeding through simple methods of recording/transcription/reading, as well as changing experiences of silence.

As critic Petra Hedler notes, "Mark So strongly embraces the phenomenon of the just barely audible, taking up a broad palette of sound-producing devices (including glasses, stones).

[6][3][permanent dead link‍] He appears on two CDs of music by composer Michael Pisaro released on Edition Wandelweiser Records: as a pianist on harmony series 11-16,[7] and contributing a sine tone to a realization of an unrhymed chord[8] produced by Joseph Kudirka.

51 THINGS TO DO WITH TWO HANDS for Eileen Myles and her Moving whole heart for Mark—which they performed together in 2011 in New York[10] and Los Angeles;[11] and a series of multi-media performance environments with artist Rick Bahto and later, with Bahto and musician Julia Holter, realized in various Los Angeles venues, including the wulf., Jancar Jones Gallery, and MOCA (2011–2013).

For more than four hours, Bahto used two 35mm slide projectors to cast two series of images—of Los Angeles area doughnut shops and cacti—onto walls, floors, and ceiling, in constantly varying rhythms and configurations, while So played a tape (Twice Around, comprising different field recordings) and performed his notebook, A Book of Palms, at the piano.

Together, they emphasized that coincidence and heightened attention are dependent upon one another, and that in concert they can take hold of the senses and direct them to their own ends, revealing unexpected beauty, symmetry, and congruencies of form.

This is the kind of awareness that arises when art is treated as an active agent of simile, a force intent on bringing disparate things into proximity.