Next weekend, Eastman double bass professor and string department co-chair James Van Demark can be heard in an unusual venue: playing his bass onstage with members of the Rochester City Ballet in the premiere of InCantation, a dance piece choreographed by Jamey Leverett to music by Adrienne Elisha. All three artists will discuss their collaboration at an interdisciplinary performance seminar this Saturday, January 25 at 3 p.m. in Eastman East Wing 415.