Well, usually (?) it means turning a piece of music (audio) into written sheet music/a score. It means that in jazz and...I believe many kinds of contemporary music. (In classical music I've heard it applied to e.g. turning an orchestral score into a piano score, i.e. an arrangement.) Here they appear to just make MIDI files, avoiding the problem of how to write the notes most readably, which is a significant part of transcription, in both these senses.
All the examples given here, though, appear to be of a super-simple variety, with dead-simple chords, all notes with robotic, mathematically-simple timing over fixed tempos produced apparently by drum machines - like toy music, the kind of music that's no challenge at all to transcribe, and in the real world I wouldn't bother transcribing by hand as there's nothing to be learnt by doing so, as you can hear exactly what's going on without it. So, that's weird.
To transfer / scribe something that you have heard. Just like a “transcript” is the written record of spoken words, transcription is the act of transferring something heads into written form.
Transcription is a valued skill among musicians. The ability to hear a piece of music and write it down can be more than a little more difficult than transcribing speech.
Not sure if apocryphal, but Mozart is known an expert transcriber, able to hear an orchestral work and write down all the different instruments as they played their parts on just one listen.
Seems conceivable. I remember a friend in high school band camp with a cassette player and a stack of manuscript paper who transcribed a Chicago song by playing a couple seconds of it, writing down all the parts and then playing the next couple seconds. I really wish I'd understood back then that this was a learnable skill. It wasn't until I was in my 30s and had a few years of choral singing under my belt that I began to develop some simulacrum of that ability.
