An Edifying Evening of Gerry Mulligan Gold.

Bill Charlap waited until almost the last possible moment in ''The Gerry Mulligan Songbook,'' a tribute at the 92nd Street Y on Monday night, before divulging a sentimental piece of trivia. It was in that room, he said, where he played his first concert with Mulligan's quartet, in 1988. The evidence suggests that it was a fine debut: a review in The New York Times singled out Mr. Charlap as ''a particularly enlivening element in the group,'' adding that ''broad gestures, even incipient levitation, helped him milk emotions from the piano.'' Mr. Charlap didn't levitate this time, but there was plenty of emotion in his solo reading of ''Noblesse,'' an impressionistic ballad from the late shift of Mulligan's career. And in many ways Mr. Charlap's bandstand experience informed the entire program, part of Jazz in July, a concert series he has produced for the last five years. [ABSTRACT FROM PUBLISHER]