Some of the music I found @ Publicdomain4u.com was originally recorded to cylinder or 78 RPM disc. Someone lovingly ripped these recordings to mp3s. Along with Michael Rosen, we worked with the digital files and tried to reduce the original surface noise, and we highlighted the music with some equalization and compression. I was pleasantly surprised with the outcome of these treatments. Many of recordings were difficult to listen to w/o this step.