Engraver action every measure with Scheme

[Ed Harbison]

Hello all! Sorry if I am doing something wrong with how to do this.  I’m new here and have never used a mailing list before, so please let me know if I should be doing something different.

I already tried asking on the Facebook group, but the only responses I got were saying I shouldn’t use Scheme.  However, I am also using this experience to learn more about LISP in general, so I’d love to get some more experience with this.

I'm currently trying to write a few scheme engravers to insert things like bar lines, rehearsal marks, breaks, and the like. I'm using make-engraver.

I seem to have been able to get breaks in with stop-translation-timestep at certain points, but it's so far only breaks that work, and apparently I have an off-by-one error at every bar somehow (which is a story for another day).

Does anyone know a way to specify a check at the beginning/end of every measure to see if something needs to happen? Like, say when it's measure 8, a break needs to happen at the end of the bar, and when it's measure 17, the beginning of the bar has a rehearsal mark accompanied with a thick single bar line.

Thank you in advance!