From Longman Dictionary of Contemporary Englishchamber orchestraˈchamber ˌorchestra noun [countable] APMa small group of musicians who play classical music together
Examples from the Corpus
chamber orchestra• Sonata for violin and chamber orchestra.• It is true that there are two solo players and equally true that Mackey matches them to a 15-member chamber orchestra.• The ensemble who are based in Caen, are the regional chamber orchestra of Lower Normandy. 