The Septet in E-flat major, Opus 20, by Ludwig van Beethoven, was sketched out in 1799, completed and first performed in 1800 and published in 1802. The score contains the notation: "Der Kaiserin Maria Theresia gewidmet", or translated, "Dedicated to the Empress Maria Theresa." It is scored for clarinet, horn, bassoon, violin, viola, cello, and contrabass. It is in six movements:
- Adagio; Allegro con brio
- Adagio cantabile
- Tempo di minuetto
- Tema con variazioni: Andante
- Scherzo: Allegro molto e vivace
- Andante con moto alla marcia; Presto
The overall layout resembles a serenade but Beethoven expands the form by the addition of substantial introductions to the first and last movements. The main theme of the third movement had already been used in Beethoven's Piano Sonata, (Op. 49 No. 2), which was an earlier work despite its higher opus number. The finale features a violin cadenza.
The scoring of the Septet for a single clarinet, horn and bassoon (rather than for pairs of these wind instruments) was innovative. So was the usually prominent role of the clarinet, as important as the violin, quite innovative.
The Septet was one of Beethoven's most successful and popular works and circulated in many editions and arrangements for different forces. In about 1803 Beethoven himself arranged the work as a Trio for clarinet (or violin), cello and piano, and this version was published as his op. 38 in 1805.