Englewood Cliffs, N.J.

Rudy Van Gelder warned his guest not to trip over the thick cables snaking along the floor as we made our way through a forest of microphone stands at the far corner of his famed recording studio. "Here it is," he said, tugging a gray plastic cover off a Hammond organ. "Nearly every organist I've recorded—Jimmy Smith, Ray Charles, Jack McDuff, Charles Earland and others—used this instrument. Many people would probably be surprised to learn that it's actually a C-3 model, not a B-3."

Mr....