Twenty-five thousand songs recorded onto 78RPM discs in the early 20th century have been released online, for free.

They are the first batch of an estimate 400,000-piece virtual record collection to be made available by the Internet Archive, from gospel by the Tuskegee Institute Sings, to opera recorded in Italy, to novelty tunes by Spike Jones, to hot — though obscure — jazz.

The task of digitizing all of those old records is happening in Chestnut Hill.

In a little storefront building on Germantown Avenue in Philadelphia's Chestnut Hill neighborhood, George Blood Audio LP, an audio preservation company, has been quietly preserving America's musical heritage, one 78 at a time.

        Listen to the George Blood digitized collection 

78 is an old format that spun at 78 rotations per minute, with grooves cut into brittle shellac. Many companies manufactured them — one of the largest was Victor Records of Camden, New Jersey — but between them there was no industry standard.

It's nearly impossible to know what the music was intended to sound like a century ago. Each company recorded their 78 records at a slightly different speed, and cut grooves that could be fatter or skinnier. Playback turntables were often proprietary to the manufacturers of the records they played.

With so many possible variations, why not have them all?

"The real thing that's different about this project is managing groove size," said George Blood, who has digitized recordings for the Library of Congress, and the Philadelphia Orchestra. "There's no standard for the size of the groove."

Blood solved this problem by developing a turntable with four tone arms, each holding a different make of stylus. On one pass of the record he can record each stylus, discretely, to its own digital track. Audiophiles are able to listen to up to 16 tracks of the same piece of music, to appreciate the subtleties of surface noise and equalization.

Blood is doing this with funding from the Internet Archive, a San Francisco-based digital library run by Brewster Kahle, who is also archiving hundreds of thousands of books and millions of web pages.

The plan is: if you build it, they will come with their own records.

"The whole project is intended to be a community effort," said Blood. "Brewster is putting forth the funds through the Internet Archive to create this reference collection to have critical mass — to have enough that everyone wants to join in. So far there are 75,000 sides that have been contributed, outside of what we have done."

All the tens of thousands of songs, and growing, are available online at The Great 78 Project.