It does not seem to work as expected, the MIDI starts when the counter goes back to 0, and stops inmediately.
I haven't used Axoloti a lot yet, closest I've used is PD, and I get a tad confused about connection types, but, as far as I understand yellow is a gate-like boolean. 'Counter''s yellow ouput's tooltip is 'carry pulse' also it has a particular symbol next to it.
I am not sure which display object would help me understand what this output spits, but I'd say it probably is a toggle that goes ON when the counter ends, and OFF right away.
As what works with the midi player is a toggle, I'd say that what I need is the opposite, something that stays ON, then goes OFF briefly, and ON again.
Perhaps I can invert the 'carry pulse' output ?