He didn't change the instrument. He didn't force the velocity. He left it at zero.
If you provide more details about the two MIDI files you're interested in, I could offer a more tailored response or discussion based on their specific qualities and characteristics. tww midi files
Elias dragged the file into his sequencer software. The timeline opened. Usually, a MIDI file is a mess of colored bars—digital representations of piano rolls, drum beats, and string sections. He didn't change the instrument