MC1270 IC double plays midis to players

CRAFTBOOK-3408 - Reported by BenButler77.1

If a midi is played via the MC1270 IC and multiple players are in the affected region, it will play the midi multiple times depending on how many players there are.
If 5 players are in the region when the IC is turned on, the players will each be played the song 5x over, causing the sound to be far too loud and notes to start cutting out.
The same thing will occur if multiple players are teleported into the IC region on the same tick.

Additionally, entering a region where a song is already playing will occasionally cause the song to restart and play multiple times depending on how many people are in the region.