The trio sonata, the most popular of middle and late Baroque instrumental forms, is a sonata for two melody instruments and basso continuo, usually a bass instrument and a chordal instrument, and consequently usually calls for four players. Trio sonatas are found at their best in the work of Corelli at the end of the 17th century. These consist of two sets of a dozen church sonatas (sonate da chiesa) and two sets of a dozen chamber sonatas (sonate da camera). There are distinguished later examples by Telemann, Handel and Johann Sebastian Bach, although the six organ Trio Sonatas by Bach interweave three strands of melody, one for each hand and one for the feet, and are, of course, for one player.