What pieces do you know like the Verdi String Quartet by composers working outside of their best known medium?

It's curious how this results in both of us grappling within the realm of Italian opera... :-)

My beloved Bellini donning symphonic tailcoat 'best bib & tucker' with his Oboe Concerto in Eb:

http://www.youtube.com/watch?v=kw8zWUyRCPA&feature...

Donizetti 'going to church':

http://www.youtube.com/watch?v=2rV4QcLuABI

And, nipping across the Alps, but sticking with opera, Schumann's singleton 'Genoveva':

http://www.youtube.com/watch?v=1kwrCKsQBXM&feature...

That last one is not so much a 'gem' as the musical equivalent of what occupied Dr Johnson's observation concerning women preachers: "Sir, a woman's preaching is like a dog's walking on his hind legs. It is not done well; but you are surprised to find it done at all."

:-)

All the best,

Great question! Because Rachmaninoff hasn't been mentioned yet I'll thrown in two of his early works that are rarely played or performed. Both are oddities in their own right. Rachmaninoff's The Bells (based on the Edgar Allen poem) and The Isle Of The Dead Also, a case can be made that his only opera, Aleko, is pretty much all but forgotten except by avid Rachmaninoff fans. (By the way, if you've never heard either The Bells or The Isle Of The Dead do yourself a favor and listen to them. Both are minor masterpieces.)

Although within his vocal medium, Rossini's Petite Messe Solennelle is a wonderful surprise to the uninitiated.

Wiki - that inconsistent and often dubious source, says the composer said it was "the last of my pêchés de vieillesse" (sins of old age). The work is for chorus, Solo singers, piano and harmonium.

Best regards.

Sibelius wrote piano music, which he not generally known for.

Chopin has some piano trios and cellos sonatas.

Puccini wrote I Crisantemi.

Mahler has an unfinished piano quartet.

Wagner has a piano sonata that's probably floating around there somewhere.

There's some chamber music by Bruckner too.

Shostakovich has a fair amount of film music.

Max Bruch's solo piano pieces are lovely.