The sixth annual D.C. Loft Jazz Festival got a late start last night and chose as its opening act one of the area's most iconoclastic performers, the solo reed player Jim Sivard.

Bent forward over the mike and speaking in a hoarse voice, Sivard maintained he had swum here from the planet Irk in the company of other Irkians. A demonstration of native speech ensued: tropical bird calls, factory quitting blasts and patrol car hoots, all produced on a small whistle.

Interspersing his bizarre, rambling monologue on extraterrestrial life with musical interludes, Sivard played a tape of garbled speech and barnyard sounds that segued into Afro-Cuban percussion. With this as a backdrop, he blew the first of several halting, disjointed and nearly interminable soprano saxophone solos.

Later, exploring the timbre and tonal character of the tenor sax, Sivard indicated that he indeed understands the instrument and in fact, has considerable skill on it. But his overall performance, utterly devoid of sensitivity or even sense, was the equivalent of a pie thrown in the face of the audience. He was all but hooted off the stage.

The Carter Jefferson Quartet and the Festival Workshop Orchestra under the direction of Carl Grubbs were to follow Sivard. The festival continues nightly through Monday.