The first demo recording on which the late David Bowie ever laid vocals has been rediscovered by a former bandmate.

Bowie, then the 16-year old saxophonist for his first band, the Konrads, was asked to contribute backing vocals to the demo in August 1963. The demo, titled “I Never Dreamed,” was recorded at Decca’s West Hamstead studios and initially rejected not only by Decca, but by Rolling Stones manager Eric Easton as well.

Long thought to be lost forever, the recording was unearthed by former Konrads drummer David Hadfield while moving in the 90s and kept secret until now. The demo is expected to fetch £10,000 (about $13,000) at auction in September. Check out a 12-second clip of the artifact below.