Upon graduation from Manhattan at age twenty he was honored with the Bronson Ragan Award for Excellence in Organ Performance. Dr. Gallagher also holds diplomas and prizes from his period of study in France, where his teachers included Marie-Claire Alain (organ), Huguette Dreyfus (harpsichord), and Jacques Taddei (improvisation). His other organ teachers have included Peter Marshall, Gerre Hancock, and Frederick Swann, Doris Hamel Eicher, and Arnold Ostlund, Jr.
Gallagher has performed as organ soloist with the Washington Bach Consort and as harpsichordist with the Chamber Music Society of Lincoln Center. He recently recorded two organ works by Curt Cacioppo for Capstone Records. He was a founding member of the Liturgical Organists Consortium, a group of five organists committed to the renewal of esteem for the organ within the Roman Catholic church. The Consortium's CD, The Sacred Legacy of Paris, won The Golden Ear Award from The Absolute Sound, America's premiere audiophile magazine. In May of 2002, the Consortium's performance in the inaugural series for the new Lively-Fulcher organ at St. Olaf Church in Minneapolis was hosted by Michael Barone and recorded for Pipedreams Live. Gallagher appeared again on Pipedreams Live in Cincinnati as part of the National Convention of the National Association of Pastoral Musicians.