Marcos is a member of the technical committees of the Association of Recorded Sound Collections (ARSC) and the International Association of Sound and Audiovisual Archives (IASA), and was part of the Collection Management Task Force that drafted the Library of Congress National Recording Preservation Plan in 2012. In 2011 he co-translated the definitive text on audio preservation, IASA's Guidelines for the Production and Preservation of Digital Audio Objects. He is a member of the Standards Committee of the Audio Engineering Society (AES), and has taught Audio Preservation at Long Island University's Palmer School of Library Science. In 2011 he mastered and restored Jacqueline Kennedy: Historic Conversations on Life with John F. Kennedy, and in 2008 was nominated for a Grammy for his work on Polk Miller and His Old South Quartette. Marcos has worked at the Alan Lomax Archives, Columbia University Libraries (where he developed AVDb, a preservation prioritization tool), the Center for Black Music Research, Masterdisk mastering studios, and Emory University. He is on the board of the New York Technical Services Librarians.