Volunteering to transcribe music of any genre, but with no commitment

Hi!
I would like to know if anyone is aware of a site, that has music waiting to be transcribed from scans to Musescore or any digital format. I think I saw something similar years ago with some chamber or classical music and was meant to help make notation for people with worse vision, I think. I'm not sure if it was volunteer based, and if so, I would love to do so, but with.. no commitment. I would hate to be volunteering with something and then made pressure on... So, do you guys know about something along those lines? Thanks in advance :)