I DO argue that this patch should be included as soon as possible.
Since macOS Sierra was released September last year, Simutrans code cannot be compiled without some tricky modification including changing MAKEFILE for more than a half year ago! This is because Sierra abolished QTKit, which is needed to play midi and wav.
However, this patch loses the volume control of MIDI. This is because AVFoundation, the alternative of QTKit, does not have the volume control for MIDI. I have to admit this does not meet the requirement of simutrans.
So, I tried to use SDL_mixier to play sound and music. It worked fine on wav, but SDL_mixier cannot load MIDI on Mac. Unfortunately SDL_mixier outputs no error message despite its loading failure.
I also tried to realize the volume control on AVMIDIPlayer but nothing useful was found.
Though pre-compiled simutrans with QTKit works fine even with the latest macOS, I worry about the possibility that Apple suddenly makes QTKit not executable. The fact that current simutrans code needs some tricky modification to compile it on Mac is a huge obstacle for new developers with Mac, and this is a loss for simutrans development community. This patch should be included as soon as possible despite its loss of volume control.