Gallagher composed the music for the successful off-Broadway show When Pigs Fly, which won wan Obie Award, several Drama Desk Awards and a Lucille Lortel Award. A song from that show, "Laughing Matters," can be heard on Bette Midler's album Bathhouse Betty. He also wrote music for the off-Broadway tuners Whoop-Dee-Doo, That's Life! and Have I Got a Girl For You!, as well as Whatnot!, which received a Richard Rodgers Production Award. His other New York theatrical credits include Back on the Boulevard, for which he served as musical director. Gallagher also worked on many concerts. In particular he had a 10-year association with Patti LuPone, collaborating with her on many of her solo shows.
Gallagher was HIV-positive and had been in and out of the hospital since May. He is survived by both of his parents, two brothers and many nieces and nephews.
There will be a viewing at the Frank E. Campbell Funeral Home from 5pm to 9pm on January 22. A memorial service for Gallagher will be held the next day at 6pm.