"Unknown Territory," the new work by Choo San Goh that will have its premiere Thursday eve ning, may be the choreographer's 34th ballet, but in another sense it's a first. Goh, the associate artistic director of the Washington Ballet, which will perform the new opus at Lisner Auditorium Thursday through Saturday, has used music of past and present eras before, but for "Unknown Territory" he's collaborated for the first time with a living composer. The ballet also marks a first for the composer -- Jim Jacobson of Chicago -- who has written music for musicals, TV commercials and pop groups, but never before for dance.

Moreover, the collaborators have yet to meet face to face. They simply exchanged creative ideas over the telephone and through the mail.

Goh explains how he came to commission Jacobson sight unseen, so to speak: "I met an associate of Jim's while I was staging a ballet of mine for the Milwaukee Ballet last year. He got me to listen to some of Jim's records, and I really liked their sound and rhythm. The style also suited the kind of new ballet I had in mind. Remember last fall I said I felt like doing something really weird? Well, this is it."

Also on the Washington Ballet's program at Lisner this week will be Goh's "Schubert Symphony" and George Balanchine's "Serenade."