“Lost” albums are often left unreleased for a reason: they’re bad. But every now and then, a little gem like this pops up, offering a valuable glimpse into an artist’s development.

The hip-hop group Atmosphere was just starting to gain recognition outside its hometown of Minneapolis, Minn., when the members began recording Headshots: Se7en in 1997. Now, they’re underground stars, and this once-rare album, originally released in 2000, is widely available for the first time.

On songs like “Tracksmart” and “@ It Again,” you can hear producer Ant perfecting his leisurely, bottom-heavy thump, while rapper Slug hones his obsession with romantic insecurity on “Swept Away” and “Molly Cool.” The 72-minute album is inflated by a fair amount of filler, but Slug’s breathless flow and self-deprecating wit deliver quotable moments in almost every song. Years later, it all still sounds fresh.

Grade: B

Headshots: Se7en is currently available.