Children's voices are written into a good deal of the operatic repertoire — the urchins of La bohème, the shepherd boy in Tosca — and small municipal choirs are what supply them. This Roman ensemble has done exactly that work, travelling out from the capital to summer opera productions on the Lazio coast; Tosca is among the operas it has served. Choirs of this kind train young singers through performance rather than through examination, and the discipline of a professional production is itself the lesson.