Beautiful Classical Smaller Pieces, duo,trio,etc

The mendhelson octet!

All of the Baroque titles on the Harmonia Mundi label, if you find period instruments "beautiful".

The Mozart Flute/Harp Concerto. Mozart clarinet concerto. Mozart also wrote a lot of chamber music for winds. I have always been struck by how beautiful and ingenious Mozart's writing for winds is. His Grand Partita is one of his most famous works for winds. In this piece he uses the Bassett Horn. Its timbre is similar to the clarinet's, but darker and has an extended lower range.

Beethoven's string quartets. Bartok's string quartets. Mozart's string quintets. Brahms string sextets are things of beauty.

A number of critics and many classical music aficionados consider Schubert's String Quintet, Op. 163, D. 956, also known as his Cello Quintet, to be the greatest piece of chamber music ever written. It's certainly among the greatest IMO.

Also, if a solo piano work is considered to be within the category that is being asked about, I would suggest Chopin's Piano Sonata No. 3, Op. 58.

Regards,
-- Al

Ptss,
Great thread Idea. Many worthwhile suggestions are/will come out of this.