(Forgotify.com)

Twenty percent of the music on Spotify has never, ever been streamed — perhaps the most striking illustration of exactly how vast and unknowable the online music catalogue gets.

But in a brilliant attempt to conquer that last musical frontier, a trio of creatives in California have launched an app called Forgotify that plays only Spotify’s never-streamed songs. They predict there are roughly 4 million of them. If we draw on the well-worn three-minute pop song cliche, that means it’ll take 200,000 people, listening one hour each, to make it through the whole catalog. Not so impossible, actually!

As for what lies in Spotify’s forgotten Internet trove, it’s a mishmash of esoterica — some of it good: lesser Mozart recordings, ’80s German rockabilly groups, the solo offerings of minor members of long-dissolved rock bands. I’m personally getting really into 85-year-old M.S. Viswanathan, apparently a prolific Kollywood composer. I have no idea what any of the lyrics are, of course, but this is pretty fun.

You can make your own Kollywood discoveries by going to Forgotify.com and logging into Spotify.