One of the best ways to explore the history of music is to find out who influenced a given artist and explore their work. In this way Led Zeppelin, The Rolling Stones and Eric Clapton would lead directly back to Robert Johnson. For this method do work one very important thing is necessary. The recordings must be available. Many older jazz or blues performances are extremely rare and only available on 78 RPM shellac discs. These discs are relatively delicate and can be easily damaged. Unfortunately until recent to these historically important performances could be lost forever. United States Library of Congress has been working on a solution. They've come up with a machine that optically reads the information on an analog disc, similar to the way that a computer scanner works. Check out the NPR story, as well as some some before and after samples. Click here for the full story.