The German word Kegelstatt means a place where skittles are being played, a bowling alley. Mozart did write that he composed the 12 duos for basset-horns (K. 487) while playing the skittles; he noted on the first page of that autograph: "Vienna, 27 July 1786 while playing skittles" ("Wien, den 27ten Jullius 1786 untern Kegelscheiben“) — only about a week before he dated this trio. However, the is no evidence that there was a similar situation with this work; the title was added by later publishers. Mozart entered this work into his own list of works as "Ein Terzett für klavier, Clarinett und Viola".
This clarinet-viola-piano trio was first played in the Jacquin's house, Anton Stadler played the clarinet, Mozart the viola, Franziska Jacquin the piano. In Mozart's time, the clarinet was a relatively new instrument, and Mozart wrote this (and his other clarinet works) for a basset clarinet (in German literature sometimes wrongly called "Bassklarinette"). After Mozart, there wasn't much classical music written for the clarinet until the 19th century.
The trio was published in 1788 by Artaria arranged for —probably with Mozart's consent— violin, viola and piano, and the original clarinet part was described as "alternative part": La parte del Violino si può eseguire anche con un Clarinetto. Due to this unusual scoring, the piece is sometimes adapted to fit other types of trios; e.g. for a clarinet-violin-piano trio, a violin-cello-piano trio or a violin-viola-piano trio as in that first publication by Artaria.
No composer before Mozart had written for this combination of instruments; in the 19th century Robert Schumann wrote Märchenerzählungen (op. 132) and Max Bruch in 1910 "Eight pieces for clarinet, viola, and piano" (op. 83).
In March 1894 the manuscript came into the possession of the musicologist and composer Charles Théodore Malherbe (1853–1911) when he bought it from Leo Sachs, a banker in Paris, who had bought it from Johann Anton André who bought it as part of a large purchase of manuscripts from Mozart's widow Constanze (the Mozart Nachlass) in 1841. In 1912 it was donated it to the Bibliothèque nationale de France, Département de la Musique, Malherbe collection, Ms 222.
The trio consists of three movements:
The Andante is written in the time signature of 6/8 time and consists of 129 bars; a typical performance would last just over 6 minutes. It does not contain any repeats, which is unusual for chamber music; among Mozart's chamber music, only the "Posthornserenade" K. 320 doesn't have any repeats in the opening movement. The most recognisable phrase of this movement's principal theme is a grupetto which appears throughout.
The opening menuetto of this movement consists of the exposition of a 4-bar theme (bars 1–12, repeated), and its development (bars 13–41, also repeated). The piano's pounding bass line and sharp dynamic contrasts set the mood of this theme apart from any conventional light and frilly notions of a Minuet. During the development, the dialogue between the instruments becomes intensified, and Mozart shows his grasp of counterpoint without ever sounding academic or "learned".
The following Trio opens with a chromatic 4-note phrase, to which the viola responds with a run of lively triplets, accompanied by chromatic chords from the piano (bars 42–62, repeated). In the development of that theme, the 4-note phrase and the lively triplets are then taken up by the piano, and clarinet and viola present some chromatically rising lines, before all three instruments start a concerto-like conversation where the 4-note phrase is only heard twice in the piano left hand (bars 63–94, repeated).
The final part of the Trio starts with a variation of the trio's 4-note phrase, which is briefly developed (bars 95–102) before returning to the brighter theme of the Menuetto whose treatment ends the movement without repeats.
The structure is AB–AC–AD–A. Theme A is an 8-bar cantabile melody in two parts, drawn from the first movement and presented first by the clarinet, then taken up as a variation by the piano (bars 1–16). The melody of theme B is played once by the clarinet (bars 17–24) before the piano plays an intermezzo of several bars. From bar 36 onwards, all three instruments play short phrases of that theme in turn, followed by a piano solo until bar 50. Theme C is presented by the viola and repeated (bars 67–76); all three instruments develop that theme in bars 77–90 (repeated). This development visits the subdominant minor scale (vi) of F minor before ending in the relative key of C-minor. Theme D is introduced in bar 116 by all three instruments almost in unison, and elaborately developed in bars 132–153 (repeated). In contrast to the previous development, this goes through the subdominant major scale (VI) of A-flat major. The movement ends with a flowery, operatic coda.