Book excerpt: This is the first in-depth study of Italian instrumental ensemble music during the seventeenth century based on the great majority of surviving primary sources. The book provides comprehensive coverage of every major composer of Italian "trio" sonatas until Corelli, and is intended as a standard work of reference. It also attempts to undermine the mythology surrounding the development of the free sonata acquired from successive generations of historians. The musical development is placed within a broad historical perspective examining such factors as performance and function.