I tried this for about 30 minutes without coming up with a single decent song. But I guess that is the whole point of an app that plays songs no one else listens to. I also cannot believe that there are so many unplayed songs on Spotify. You would think that at least friends of the artist listen to these songs. An app that shows songs that are just about to become popular (kind of like newswhip.com for viral stories)…
I've found that http://old.thesixtyone.com/ is a good site for discovering new music. (You want the "old" interface because it's so much more usable than the new one.)
Some of the bands that I learned about on thesixtyone became huge hits a year or two or seven later -- fun. and Passenger come to mind. Of course many of them were never heard from again, as well.