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The idea first came to Lane Jordan when he heard an odd little fact: Around 20 percent of tracks on Spotify—some four million songs—had been played exactly zero times.

Four million songs! That got Jordan thinking. What were those songs? And don't they, too, deserve a little listening?

Jordan brought the idea to his friend, J Hausmann, and together, along with the help of a third friend (Nate Gagnon), they built Forgotify, a discovery engine for Spotify's unplayed tracks.

Forgotify is built upon a database that the trio created to crawl Spotify's API for pieces with a play count of zero. Once a song has been played, it disappears from the site, rendering it oddly reminiscent of an old, archival audio cassette which, once played, may never play again. Playing it destroys it. (Except, of course, in the case of Forgotify, the songs still live on in Spotify proper.)

The catalog of zero-play songs is, unsurprisingly—definitionally, perhaps—obscure. I've been listening to it for the past few hours, and its finds have been ... eclectic, with a few hits mixed in with lots of misses. There's been operatic French modernist music, instrumental church hymns, one bit of Tchaikovsky (something of a reprieve), a country ballad sung by a New Zealander during a brief Nashville sojourn, Greek rebetiko, and a Norwegian religious folk melody played on a recorder (the clear winner, in my book).

One of Forgotify's recent picks for me (Forgotify)

According to Jordan, a lot of Spotify's undiscovered tracks are older: Newer music tends to get at least a few plays as it posts, but the backlog from decades past just sits on Spotify's digital shelves, accumulating dust. Forgotify, however, is built to mix it up. "We’ve tried to randomize the plays as much as possible so that each sequential track is from a different era and genre," Jordan told me.