Almost 20 years ago composer John Eaton and electronic-instrument designer Robert Moog devised a keyboard that would allow the performer better control over a wide range of sounds. At the time Moog had already come up with a first-generation synthesizer, named after himself and made famous by Walter (now Wendy) Carlos. This pioneer effort inspired the models now used by rock 'n' rollers and commercial jingle writers; the Eaton-Moog Multiple-Touch-Sensitive Keyboars, however, is an even more intricate apparatus with keys that respond in various ways according to finer pressure. (I'm told it's intended for performers with the dexterity of an organist.) At this instrument's debut concert, two keyboards will be stacked like an organ console, and they will interface via computer with three synthesizers that produce sounds digitally and analogically. Eaton's brief piece, aptly titled "Genesis," demontrates the uncommon versatility of the keyboard which Eaton hopes will put more sounds at a composer's disposal. Along with Microtonoal Fantasy, a duet for pianos tuned a quarter tone apart, on this all-Eaton program in Peer Gynt, a theatrical "romp" based on Ibsen's retelling of the Norwegian folktale. The instrumentalists of the New York New Music Ensemble, under the direction of Mike Phillips, will also act, sing, and mime; in fact, the clarinetist is expected to execute a somersault while playing. Tonight, 8 PM, Mandel Hall; 1131 E. 57th St. 702-8068.