[Midi] Choppy sound with multiple files

Hi there! 

I was able to get this working in 1.12.2 Open computers with applying these changes here:
https://github.com/OpenPrograms/Sangar-Programs/pull/19/files

However, the sound is very choppy no matter what file is played. Is this as expected or is there a way to improve the sound fidelity? (Namely, the notes and stuff are all correct but it plays them too slowly or badly timed)