premise: Keeping the mood light , the two then chanted and chortled their way through some murderous polyrhythms , devised by Mr. Douglas as an alternative to Hindemith 's dry theory-teaching techniques , and then , with Mr. Gomez , soared and improvised on the composer 's tight `` Bebop Etudes . ''
hypothesis: The composer 's tight `` Bebop Etudes describes the location of the improvising.