I would go even further and say that, once [Stephen] Sondheim had ceased to compose classical music with its nonspecific accompaniments, he began to explore how effectively a vamp can flesh out a character for the stage. He had little need to write distinctive vamps for his Williams [College] shows, but already in 1954—before the highly characteristic vamps in West Side Story—we see him growing in his ability to get under a character's skin through his accompaniment.