Mr. Mackenzie has been hailed by The New York Times as Robert Shaw's "designated successor."

In his 14-year association with Shaw, he was keyboardist for the Atlanta Symphony Orchestra, principal accompanist for the ASO Choruses, and ultimately assistant conductor for those choruses.

In addition, he was musical assistant and accompanist for the Robert Shaw Chamber Singers, the Robert Shaw Institute Summer Choral Festivals in France and in the United States, and the famed Shaw/Carnegie Hall Choral Workshops.

In 1996, Mr. Mackenzie made his New York conducting debut in a Carnegie Hall sponsored concert, leading the Robert Shaw Chamber Singers in a critically acclaimed performance at the Cathedral of St. John the Divine, substituting for Shaw on short notice.

In 1999 he was chosen by Shaw to prepare the Carnegie Hall Festival Chorus for Charles Dutoit, when Shaw was unable to conduct, and he was choral clinician for the next three annual workshops.

A native of suburban Philadelphia, Mr. Mackenzie made his debut as a pianist with the Philadelphia Orchestra at age twelve, and as an organist at age twenty.

He made his New York recital debut at the Fifth Avenue Presbyterian Church. He holds degrees from the University of the Arts in Philadelphia and Westminster Choir College.

He has prepared choruses for performance under Robert Spano, Donald Runnicles, Roberto Abbado, John Nelson, Alan Gilbert, Yoel Levi, Robert King, James Conlon, and Sir Neville Marriner.

Mr. Mackenzie is a frequent recitalist at conventions of the American Guild of Organists and clinician for those of the American Choral Directors Association. He has been regularly featured on National Public Radio's Performance Today and Minnesota Public Radio's Pipedreams.

His performance of the Stephen Paulus Organ Concerto No. 1 can be heard on the CD Pipedreams Premieres, Vol. 2. Mackenzie’s acclaimed Telarc recording of a cappella sacred music (featuring the Vaughan Williams Mass in G-Minor) represents the ASO Chamber Chorus’ first recording apart from the orchestra.