BIDDEFORD, Maine – A 120-year-old wax-covered cylinder containing the earliest known recording of a black vocal group in the U.S. was sold at auction Saturday.

Discovered in a private collection in Portland, the 1893 recording of “Mama’s Black Baby Boy” by the New York-based Unique Quartet was one of only two copies known to exist and sold for $1,100. The other resides in the Library of Congress.

A second Unique Quartet song, “Who Broke the Lock (on the Henhouse Door)?” from 1896, sold at the same auction for $1,900. The same buyer purchased both recordings, which pre-date vinyl records.

The recordings were so rare that auctioneers at Saco River Auction Co. had no idea how much they might fetch. An appraiser had suggested they were worth $25,000 or more each before the auction.

The cylinder recordings were played on an early-style phonograph that had the appearance of a Victrola-style player. But the music was etched in wax on cylinders instead of in the grooves of vinyl records, which were popular throughout the 20th century.

The wax was so fragile that auctioneers didn’t dare try to play them.

Robert Darden, who’s working to save black gospel music by digitizing existing vinyl recordings through the Black Music Restoration Project, said all pre-digital black sacred music is at risk, including music on cylinders, vinyl 78s, 45s, and LPs, and cassette recordings.

In World War II, for example, many cylinder recordings and vinyl 78s were melted down and recycled to support the war effort, said Darden, a professor at Baylor University.

“As a country, we just don’t have a very good track record of recognizing, preserving and celebrating this music, this art form,” Darden said.