Indeed it described an output and was also a UI. I meant that describing the output could be the UI. I pictured a textbox or a whisper-style text to speech session. Basically an ai chatbot specialized for generating music.
I couldn't figure out precisely what that video showed, but it was fascinating.
Somehow it reminded me of the orca music programming environment.
https://www.youtube.com/watch?v=r28Xy-1_F8I
https://www.youtube.com/watch?v=-tAAsolMG-M