WHEN a five-alarm fire ravaged Manhattan’s Central Synagogue nearly four years ago, the music died, too: Lost in the ashes was the Reform congregation’s organ, crushed under a fallen beam.

The music is back.

At 8 tonight, the temple, at Lexington Avenue and 55th Street, will unveil its new, state-of-the-art pipe organ in a free public concert by organist David Higgs and the Orpheus Chamber Orchestra.

On the program: Bach’s Passacaglia and Fugue in C minor and several other works.

Seating is first come, first served. For more information, call (212) 838-5122.