T50029: crackling at start of OGG renditions of MIDI files (fixed in TiMidity++ 2.14.0) describes a problem that occurs with the TiMidity++ package currently used by MediaWiki-extensions-Score. @Stemby proposes in T50029#2494744 to switch to fluidsynth.
TiMidity++ does not seem to be maintained very much (https://tracker.debian.org/pkg/timidity) compared to fluidsynth (https://tracker.debian.org/pkg/fluidsynth) while the latter can still perform the MIDI->OGG (or MP3: T181875) conversion.
This task also affects T135597: Move MIDI to audio conversion from Score into TimedMediaHandler as it would no longer be TiMidity++ but the new package.