Composer and musicologist, he studied composition with Muhal Richard Abrams at the AACM (Association for the Advancement of Creative Musicians) School of Music in Chicago, and trombone with Dean Hey. He also graduated in philosophy from Yale University. Member of the AACM since 1971. 

In 1980–82 he was the music director of The Kitchen centre for avant-garde and experimental art in New York. For 12 years from 1991 he taught at the University of California in San Diego, where he coauthored the Critical Studies/Experimental Practices programme. Since 2004 he has been a professor at Columbia University, where he serves as Area Chair in Composition and member of the faculty in Historical Musicology. He currently serves as Artistic Director of the International Contemporary Ensemble. As a performer and improviser, he has collaborated with artists such as Anthony Braxton, Derek Bailey, Joëlle Léandre, Miya Masaoka, Frederic Rzewski, Yuji Takahashi, John Zorn, as well as Count Basie’s and Gil Evans’ orchestras. Lewis’s work in electronic and computer music, multimedia installations, notated and improvised forms has been documented in more than 150 recordings and sheet music, published by Edition Peters. His compositions have been performed notably by the BBC Scottish Symphony Orchestra, Philharmonia Orchestra, Radio-Sinfonieorchester Stuttgart, Mivos Quartet, the Boston Modern Orchestra Project, the London Sinfonietta, Spektral Quartet, Talea Ensemble, Ensemble Dal Niente, Wet Ink, and many others. He has received numerous commissions from prestigious festivals such as the Venice Biennale and BBC Proms, as well as orchestras and ensembles. Lewis is a Fellow of the American Academy of Arts and Sciences and the American Academy of Arts and Letters, a member of the Akademie der Künste Berlin, and a Corresponding Fellow of the British Academy. 

His book A Power Stronger an Itself: The AACM and American Experimental Music (2008) won the American Book Award and American Musicological Society’s Music in American Culture Award. Lewis and Benjamin Piekut are the coeditors of the two-volume Oxford Handbook of Critical Improvisation Studies (2016). An Honorary Member of the American Musicological Society, Lewis holds honorary doctorates from the University of Edinburgh, New College of Florida, Harvard University, and the University of Pennsylvania. 

Selected works: Shadowgraph, 5 for improvisors with open instrumentation (1977), Voyager, interactive computer music work (1987, continually revised), Artificial Life 2007 for improvisers with open instrumentation (2007), Anthem for voice, chamber ensemble and electronics (2011), The Will To Adorn for large chamber ensemble (2011), Mnemosis for septet (2012), Assemblage for nine musicians (2013), Memex for symphony orchestra (2014), Emergent for flute and computer sound processing (2014), Afterword, opera to the composer’s own libretto (2015), Minds In Flux for symphony orchestra and spatialised computer sound processing (2021), Amo for five voices and spatialised computer sound processing (2021).