In addition to duets and trios, we (a hardy subset of Cowley Orchestra and some newbies) have also played some quartets over this summer. These included baroque pieces set for three melody instruments plus basso continuo (Baroque composers didn't mind very much what melody instruments were used). On some meetings, when we had a strong ensemble, we also ventured into the string quartets of classic/romantic periods.
This Bank Holiday Monday we had a particularly strong ensemble (nothing to do with me, I am either the weakest link or hiding behind a stronger player) with an interesting variety of instruments and played Dvorak's American quartet among other things. It struck me that I actually prefer our version with five different instruments (violin, flute, oboe, clarinet on the viola part, cello) to the string quartet performance. Listening to string quartets, I don't really like the fact that the four string instruments have similar sound textures and all blend into one sauce - having a variety of different sounding instruments is actually an improvement to me. Also, with its richness of textures, the random instruments version is a lot closer to the New World symphony.
(UPDATE 11.9.2021: Just discovered it's been done before. Somebody called David Walter arranged it for wind quintet (flute, oboe, clarinet, bassoon, horn, published by Billaudot - Paris 1986) and YouTube has live videos from the Amsterdam Wind Quintet (fourth and first movement) as well as sound-only recordings from the Royal Flemish Philharmonic (complete) and Meliora Winds.)
Anyhow, here's my nascent collection of quartets so far:
Boccherini: 9 string quartets (various opus numbers).
Dvorak: string quartet No. 12 in F major (American quartet)
Haydn: Quintenquartett Op 76, Nr. 2, in D minor
Pachelbel: Canon in D, arranged for string quartet by Donald Fraser
Schubert: Excerpts from 5th symphony, strings pack
Schubert: Quartet for flute, guitar, viola and cello (YouTube). Found this in an edition published 1956 - it later turned out that Schubert had just arranged a trio by Czech guitarist Vaclav Matiegka (1773-1830) and added the cello to give it a bit more oomph. The original trio (Notturno op 21) is lovely, actually, but doesn't harm to have the cello part too.
Shostakovich: String Quartet No. 1 Op 49.
And a bunch of baroque quartets I borrowed for the summer:
MA Charpentier, Noels (9 short pieces, some christmassy)
Naudot, concerto in C major
A. Scarlatti, Sonata in F major
GP Telemann, concerto in G major
JB Fasch, quartet in Bb major
JC Schickhardt, sonata in D major
The last page of the autograph score of Dvořák's American quartet with his inscription: "Finished on 10 June 1893 in Spillville. Thanks God. I'm satisfied. It went quickly."
Updated 6.9.2021 to add the Schubert quartet based on the Matiegka trio.