There are singers looking for songs and writers looking for singers on DigiRAMP. 
Maybe a kind of notification system could be helpfull?

I was dreaming about creating something I will call a 'Music project' 
A little closed group where you can invite people to do certain tasks, e.g. program a bass, write some lyrics.
Everything should be well organized and related to music production with the legal framework in place
File sharing, project management, calendars, notifications e.t.c

Why not hook up graphic artists with musicians. behance.net could be a nice partner