In the good old days, the worst that could happen during a concert was a broken violin string. Last night at the Corcoran Gallery, the computer went down, forcing an intermission when none was planned, in the middle of the only piece on David Behrman's program.

Behrman is a musician-computer whiz, or vice versa, who, armed with an Apple II computer, an assortment of synthesizers, floppy discs, video monitors, home-made, computer-controlled guitars and real, live flute players, has been investigating the possibilities of live performance of electronic music. Where the cold impersonality of a tape recorder used to provide the electronic component of such music, in days not so long past, Behrman now serves the same function, but in a much companionable way, by fingering the circuits on his "guitar" as he sits with the rest of the ensemble, both electronic and live.

Last night's concert, the second in the 9th Street Crossings series, featured Behrman's "On the Other Side of the Ocean," a duet, about an hour long, for all sorts of flutes with an electronic pedal background that sounded a good deal like an organ much of the time.

Flutists Robert Dick and Steven Gorn had at their disposal a marvelous assortment of instruments that ran the gamut from bass flute to ceramic whistle. On them, the two managed an enormous variety of sounds, many of which God certainly never intended a flute to make. Much of this seemed improvisational in nature, although, clearly, there was a sense of tight ensemble, and it appeared that whatever instructions they were receiving came from the video monitor.

The music had a sort of hypnotic charm, although it must be admitted that this charm began to pall after 20 minutes or so. The live performers were admirable, and, after a re-run through the programs on the discs, the Apple revived and did its job also.