hi Mike,
Believe me, you'd get a lot more satisfaction by doing this the more discrete way rather then resorting to a micro. Microcontrollers can be tedious to learn and hard to get the parts for it to program and the support components (crystal, caps).
But if you feel that you have the time, money, and initiative to it, go for it!
If I were you, I would take the suggestion about using a low and high frequency oscillators with two binary counters. This would give you several frequencys to play with without the cost of making several oscillators.
Steve