Marc Lowenstein is an active conductor, singer, composer, and teacher. He has conducted for the last two years on New York City Opera's VOX showcase festival. He also conducted the premiere of Anne LeBaron's WET. He was music director for the US premiere of Georges Aperghis' Sextuor: L'Origine des Espèces and for the premiere of Stephen Oliver's Peach Blossom Fan at the REDCAT theater. In addition, Marc was a founder and director of Berkeley Contemporary Opera with whom he conducted the premiere of Martin Herman's The Scarlet Letter and performances of several other modern operas.

In Los Angeles, Marc conducts regularly with Ensemble Green, the Vinny Golia Large Ensemble, and the CalArts New Millennium Players with whom he has led American premieres of several works by composers such as Gavin Bryars, John Oswald, Henry Brandt, James Tenney, David Rosenboom, Wadada Leo Smith, Kubilay Uner, Mark Menzies, and many others.

As a lyric tenor, he recently sang the lead tenor role of Madeline X in the premiere of Michael Gordon's What to Wear directed by Richard Foreman at REDCAT. Marc has sung about twenty-five other opera roles including Pelléas, Don José, Oedipus, Tom in A Rake's Progress and Sandy in To the Lighthouse. Despite working in opera for so long, he has nonetheless himself written a full-length opera, The Fisher King, based on the screenplay of the same name; and he has begun one based on the short stories of Charles Bukowski. He has also written several other large works.

On the faculty of the California Institue of the Arts, he teaches theory, skills, history, composition, voice, and conducts various ensembles.