What's the best way to turn pure data output into sheet music? I saw one person talk about using rosegarden, but was having problems with that, and people have talked about musicxml but I don't see an actual library. Is there any way to (a) generate musicxml, or (b) route to museScore or rosegarden?

Thanks!

I would look at jack, and specifically it's interface qjackctl. If you are running Mac or Linux, it can handle midi patching for you. I use it to route midi out of PD and into rosegarden all the time, and vice verse too.

Alternatively, if you're on a mac, look at setting up an IAC bus