Apology for the slight detour, I wonder if pianists/drummers have a leg up on this. The multiple parallel layers (hands/melody/chords for piano, polyrythms mapped over all limbs). This forces your brain to handle many things at once yet focus on a single whole. In my small experience it was highly meditative (and very deeply stimulating for the brain).
Don't apologise, I've wondered the same thing many times! One way of categorising meditation is single pointed (basically, one object of attention) and many pointed (many objects, usually contemplative and attempted after skill in single pointed techniques, though not always - vipassana as an example), though one can become the other. I'm not sure that something with many things to concentrate on will help foster levels of concentration (jhana) better. <y feeling is they probably just help keep it interesting, which is an underrated ingredient - even things we like and enjoy can feel like work if we feel we should do it, or have to do it, or we get no variety. Music provides variety, energy and spoteneity in abundance.
It's also very distracting too. You can't have it all :) Personally, I've found learning scales or some particular run of notes to be similar to single pointed meditation but I notice changes in mental state more with a traditional technique, my goals are slightly different.
> even things we like and enjoy can feel like work if we feel we should do it, or have to do it, or we get no variety
This is what modern society produces. I often try to turn chores into joy, or games. When you think about it, the difference in labour and fun is small.. Doing 200 pushups or 200 wipes on the floor, both can be nice and beneficial. People should frame stuff this way. The issue is that social structures make that difficult, you can rarely tell your boss "hmm i'm gonna do it this way because I feel better" your 'self' has no place in a work group so you become a slave and suffer.
A lot of people consider music like a semi transe. Drums are special because of the apparent simplicity in gesture and sound, but even broken scales can be deeply infatuating.
