Why 78rpm, 45rpm, and 33.3rpm?

Here's a link Lugnut was kind enough to provide in another thread. http://www.ifrance.com/c-i-f/hificol.html

Not sure about the rest of it but look forward to reading some responses.

Actually, I think the CD sample rate was chosen because (as I understand it) because you need a sampling rate twice the highest frequency recorded. The rate is higher than that, probably to give room for error or some such thing.

As for records, I'm under the impression that there were several different speeds in the "78" era. It was probably a case of doing whatever worked the best for a given company.

I've no idea about the 33.3 and 45 speeds. I have heard that the 33.3 was the Columbia standard, and RCA adapted the 45 RPM speed so that they could have their own format. I wonder, though, if the 33.3 RPM choice might have been made on the basis of playing time--that is, trying to get a 12" record to play for "x" minutes a side.

There is also 16 RPM. You will find some vintage German Dual Turntables that play all four formats....