Please recommend some classical music...

I’m using the generic term, so not just music from the Classical Period. Anything on the darker/heavier side (if that makes sense) with lots of singing, preferably solos or choral singing that could be done relatively easily as a solo.

If it helps I enjoy Schubert, Mozart, Saint-Saens, Donizetti, and others.

Any suggestions would be greatly appreciated.

The Essential Music Library: Classical

Try Gustav Mahler. I like the Symphony #8, Symphony of a Thousand.