Printed sources of pre-Corellian trios include several distinct scorings, one of which requires four performers (SSBbc). Particular scorings correlate with musical style and function. Melodic bass and chordal continuo were employed in the church sonata; one or the other in the dance repertoire. Moreover, the stronger the contrapuntal role of the bass part, the more likely it was to be played on a melodic instrument. After 1660, sacred and secular scoring practices became less distinct. Increasingly active dance bass lines were more often figured, while chordal and melodic bass parts of church sonatas became nearly identical.
"The Trio Sonata in Pre-Corellian Prints: When Does 3 = 4?,"
Performance Practice Review:
2, Article 4.
Available at: http://scholarship.claremont.edu/ppr/vol3/iss2/4