The show had started well before Hector Olivera ever appeared on the scene at the Capital Hilton's Presidential Ballroom Sunday afternoon. His nine-manual organ-synthesizer, with three consoles and a dozen or more speaker systems, the whole surmounted by a huge mirror (all the better to see the keyboard action), sat on stage blinking frantically as red and yellow lights signaled some message of electronic import. Below, at the foot of the stage, a bust of Beethoven glumly surveyed the aisle.

This was another in the series of Beethoven Society Pops Concerts given here from time to time, and Olivera entertained his receptive audience with a dazzling display of sonic and technical marvels.

Olivera built the machine (he calls it the "0-1 Orchestra") to approximate the sounds of nearly all the instruments used in western music, and on it he whomped up imitations: of an orchestra playing Tchaikovsky's "Light Cavalry" Overture and the hit tune part of Rossini's "William Tell" Overture; of the '40s big band sound; of a jazz band; of a marching band; and of a synthesizer playing "Clair de Lune" (wait -- that was no imitation, that was a synthesizer). Sometimes he set automatic rhythm backgrounds in motion and grooved to the beat. He seemed to revel in all the action.

After intermission he returned for a performance of a Symphony Concertante by Joseph Jongen for organ and orchestra, arranged here for organ and organ. To be more precise, Olivera played a more traditional electronic organ (that was also on stage) to the taped accompaniment of himself playing the orchestra on the "0-1." Here the balance and ensemble were fine, but it was a little hard to separate out the sounds of the two organs.

Olivera is an engaging entertainer who, clearly, has found his particular niche and fills it splendidly.