"Theory and Practice of Piano Construction" by William B White, is where I got the method. It's around here somewhere... Essentially, you start with the natural logarithm of C-8 speaking length, chose a number (try 0.02 as an example) as a progression rate, add this number times the number of notes below C-8 you are to the original Ln(C-8 length), and take the exponential of the number. The semi-log progression rate is determined by your chosen multiplier. Try it. You'll figure it out. Start checking the scale progressions you find in pianos against this method. It's interesting. Even what seem to be semi-log progressions aren't necessarily the same progression rate throughout the scale, and very often change below the first two octaves. Another handy source of confusion. Ron N
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