This site is mainly about the 20th century Russian and Soviet pop song. First of all, it allows to find different versions of songs and compare them.

See also:

Russian-Record.com - you can listen to phonograph records

Sheet music in the National Library of Russia - you can see file cabinet in Russian, not full documents
Sheet music in the Russian State Library - you can register and buy scanned sheet music

Rustam Fakhretdinov, dzanni@gmail.com