Kieren enjoys an active musical career on both sides of the score.

As a composer and arranger, Kieren is regularly commissioned by artists and organizations around the world. His catalogue includes musicals, chamber operas, film and theatre scores, pieces for solo instruments and ensembles, vocal and choral works, spoken word compositions, and concert-length multidisciplinary works. Many of these have received feature performances at international music conventions and festivals, as well as broadcasts on national, regional, and internet radio. Numerous recordings are currently available on compact disc or for digital download.

Kieren's musical dramas — seen by thousands of people throughout Canada, the United States, and the United Kingdom — have been called "brilliant" (Mark Kanny, Pittsburgh Tribune-Review), "a new kind of musical theater…smart and moving" (Andy Druckenbrod, Pittsburgh Post-Gazette), and "a new, stunning body of story and sound, that left me deeply satisfied and piqued" (Sequenza21). In additional to being perennial audience favourites, these works have garnered many critical awards, including Outstanding New Play and Outstanding Production for Young Audiences (NOW Magazine), Top Ten Concerts in Pittsburgh (Pittsburgh Post-Gazette, 2006 and 2008), and a Total Theatre Award nomination (Total Theatre Edinburgh).

Kieren is also in demand as a pianist, singer, and musical director, averaging over one hundred performances and appearances each year. Recent productions he has music directed include Robin Hood: The Legendary Musical Comedy (Hart House), West Side Story (Randolph Young Company), The Musical of Musicals: The Musical! (Ontario premiere, Gypsy Theatre/Bluewater Playhouse), Hats! (Canadian premiere, Stirling Festival Theatre), and The Great American Trailer Park Musical (Toronto premiere, Hart House Theatre). For the past four years, Kieren has been co-creator and Music Director for the holiday panto at Stirling Festival Theatre, seen live by over ten thousand people annually.

In addition to private vocal coaching, Kieren has been on the faculty of many vocal and choral festivals and camps (StArt Youth Presenting Art Festival, New York State Summer School for the Arts), has been invited to give guest lectures and lessons at several universities and colleges in Canada and the U.S., and was the inaugural Keynote Speaker at the University of Colorado–Boulder's Entrepreneurship Center for Music. Currently, he is a faculty member at Toronto's Randolph Academy for the Performing Arts.

Kieren received his B.Mus. at the University of British Columbia, and his M.Mus. from the Shepherd School of Music at Rice University, where he studied with Paul Cooper and Samuel Jones. He now lives in Toronto with his wife Lada Darewych and their daughter Marianna.