writes some fascinating music for the theater and his between-scene music in the Geffen Playhouse's production of Wendy Wasserstein's "Third" grows progressively intriguing as the evening wears on. Play takes place during the course of a school year, beginning with breezy autumnal themes that teeter toward new-age stream of conscious composing. Guitar and acoustic bass are the key instruments with  strings adding textures, as the drama develops and winter sets in, Roth's music ushers in moods that not only echo the previous scene but hint at the action about to come. It is music that deserves a future.