Wow, what a trip. I never knew there were records that modulated up and down. I assumed the recording cylinders did, because I've seen the recording mechanism. Now that I think about it, it makes sense that there would be a progression from that to disk that modulated up and down. I just never thought about it, and didn't know of such a beast.I remember the old ceramic cartridges had two-sided needles that flipped over for 33/45 and 78 RPM operation. I assumed the issue was groove width, but never looked into that either. Do you know if that's the difference? If not, do you know what is?