Well, I meant to get to adding actions to my grammar. But I have a great excuse for not making progress. At the moment, there is a big push underway in Rakudo development to replace the current master branch with the ng branch. As I understand it, ng implements actions a bit differently than master -- it is more true to the Perl 6 spec. But right now, ng isn't ready to use, and there's not much point in targeting an out-of-date implementation that is going to go away in the next couple of weeks. So I'm putting this on hold until ng is in place.
If you're following along at home, I did go ahead and add grace notes, chords, nth endings, and rolls and staccato markings. It's so straightforward it's not really describing how I did it, but it is uploaded to github if you'd like to try it. I don't know if it will properly support Irish music yet, as a commenter requested last time, but it ought to be closer, anyway.