Conversation so far:
What happened in the late 1930s for Duke Ellington?
From 1936, Ellington began to make recordings with smaller groups drawn from his then-15-man orchestra and he composed pieces intended to feature a specific instrumentalist.

Question: who was a part of the gorups?
Self-contained rewrite: Who was a part of the group Duke Ellington worked with in the later 1930s when Ellington was more focused on composing to feature a specific instrumentalist?