When I got hi as a teenager I’d hallucinate the most intricate music you could imagine but with no way to “record” it. Would be fascinating if we one day had the means to tap into visual and audible hallucinations (perceptions) in the brain.

There is a Github somewhere that recorded EEG of people listening to simple piano melodies, I'll see if I can find it.

Edit: I found some things!

1. A paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541010/

2. A list of datasets: https://github.com/ismir/mir-datasets