From at least the 19th century on, the term "string trio" with otherwise unspecified instrumentation normally refers to the combination violin, viola and cello.
Over the course of the late 18th century, the string trio scored for violin, viola, and cello came to be the predominant type.
[1] Most movements were in binary form, although some of Joseph Haydn's trios were written as theme and variations.
The violins shared the important thematic material, while the cello maintained an accompanimental role.
Inspired by the piece, Beethoven set out to write String Trio in E-flat, Op.
[3] The concertant trio was created in France, consists of two movements, and all three voices are used equally in the texture.
[3] Some of his works include 3 trios concertants pour violon alto et violoncelle, Op.