Sentence:  Of course , it must not be forgotten that in achieving this historical feat , Prokofieff had the vast resources of his people behind him ; time and economic security ; symphony orchestras , opera and ballet companies ; choruses , <WSD>chamber</WSD> music ensembles ; soloists ; recordings ; broadcastings ; television ; large and eager audiences . 
Meaning of the word marked with <WSD> tags:  serious music performed by a small group of musicians