It's a fairly simple task to email a mix for someone to add parts, and send back to the writer your extra parts. I do it a lot for clients and friends.

In all fairness, I don't mind if it is arranger drums, or DM10 patterns with overdubs (yours sounded fine) or whatever it is, I wasn't really thinking put a first call album together! Just that, it would be fun to lay a part or two down on something you send, back and forth, that kind of thing. Maybe, only after we have tried it for fun a couple of times would it be worth pushing it to the next level if it shows promise...

Thing about it, as far as I am concerned, would be to limit it to just a tiny bunch of us, especially at first. Open collaboration like this can easily get out of hand if it opens up too much. Maybe later, once the flow is worked out...

Email me privately, if you want to work out in more detail how this is doable. Just remember, I'm kind of suggesting this as just a casual fun thing, nothing major. Just two old guys having fun