Human singing creates overtones that register as extra notes.

MIDI files contain musical information, such as notes, rhythms, and chord progressions, which can be used to recreate a song using virtual instruments or hardware synthesizers. This format is incredibly versatile, making it a popular choice among music producers, composers, and arrangers.

What (piano, guitar, vocals) are you converting?

Converting a YouTube video to MIDI is relatively straightforward. Here's a step-by-step guide using Online-Convert: