Project Gutenberg Europe currently doesn't digitize sheet music.
Project Gutenberg volunteers have been engaging in digitizing public domain sheet music, using a variety of techniques, to enable study and performance. For the most part, the musical pieces created have been chamber music, with composers such as Brahms and Beethoven.
Thanks to ClassicalArchives.com, source of musical performances for many composers, in many formats. ClassicalArchives.com worked with Project Gutenberg on our sheet music subproject. Project Gutenberg also received a donation from an anonymous family foundation to help start the sheet music project.
Interested in other similar projects? We recommend Mutopia Project, which has many pieces of sheet music.