As I was entering Robbie's formula for converting MIDI number to
frequency into my Palm Pilot (which is where I put almost every
interesting piece of information these days -- I got tired of losing
little pieces of paper!), I thought I would share this tip. There's
software called MathPad which allows you to solve just about any
formula on your Palm Pilot. You can try before you buy. See
Here's Robbie's formula, as entered into my Palm Pilot. The "n:79"
indicates that "n" is input, "f->" indicates that "f" is to be output.
MIDI note number to F
Another example illustrates a very valuable feature: you can reverse
the roles of the variables without rearranging the formula. Consider
the formula for capital recovery. Given any three of the variables
i (interest), n (period in years), r (monthly payment), and p
(principal), you can calculate the fourth.
For example, how much can I borrow if I can pay $600/month for 5 years
at 7% interest? Note how this works. Since r, n, and i are input,
the principal p can be calculated without having to solve the formula
Mortgage (monthly crf)
I use this tool so often that I can't live without it anymore. Anybody
interested in science or engineering should find it useful, too.