Principal chamber music genre of the Baroque era. Despite its name, it requires four performers: two melody instruments and continuo (usually a keyboard instrument and a bass instrument). It arose early in the 17th century as an instrumental version of the Italian vocal-duet ensemble. The two upper instruments, usually violins, generally wove their melodic, quasi-vocal lines high above the accompanying parts. Two standard forms emerged after 1750: the sonata da chiesa, or church sonata, standardized as a four-movement form (in slow-fast-slow-fast order); and the suite-like sonata da camera, or chamber sonata. By 1770 the genre had been abandoned in favour of the solo sonata