I would have thought that I had pretty mainstream music tastes, but not according to this tool – I’m only 14.68% mainstream which is WAY cooler than like being 80% mainstream or something. It works using Last.fm which I’ve found to be a bit flakey in taking music submissions recently, but I’m hoping they’ll sort that out.
If you want to get Last.fm working for you, check our their guide here. It’s a neat site, and is good for finding you new music! My profile is here if you want to see what yours would look like.