DETROIT (AP) ― Detroit is famous for its music, from the Motown hits of the 1960s to the cutting-edge punk of Iggy Pop to the rap of Eminem. Little known, though, is that Michigan was also fertile ground for folk music, brought to the region by immigrants in the early 20th century and played in the logging camps, mines and factory towns where they worked.

Legendary folklorist Alan Lomax discovered the music in 1938 when he visited the Midwest on his famous 10-year cross-country trek to document American folk music for the Library of Congress.

A trove of his Michigan recordings is now being publicly released for the first time by the library, coinciding with the 75th anniversary of Lomax’s trip. The release is causing a stir among folk music fanciers and history buffs.

“It was a fantastic field trip ― hardly anything has been published from it,” said Todd Harvey, the Lomax collection’s curator at the library in Washington. The Michigan batch contains about 900 tracks and represents a dozen ethnicities.

Lomax, son of famous musicologist John A. Lomax, spent three months in Michigan on his research, which also took him through Appalachia and the deep South. He drove through rural communities and recorded the work songs and folk tunes he heard on a large suitcase-sized disc recorder powered by his car’s battery.

The trip was supposed to cover much of the Upper Midwest, but he found so much in Michigan that he made only a few recordings elsewhere in the region.

The collection includes acoustic blues from southern transplants, including Sampson Pittman and one-time Robert Johnson collaborator Calvin Frazier; a lumberjack ballad called “Michigan-I-O” sung solo by an old logger named Lester Wells; and a similar lament about life deep in the copper mines of the Upper Peninsula called “31st Level Blues,” performed by the Floriani family, who were of Croatian descent.