Actually digital will be much easier, in the meaning of just a square wave, you can use that(after some conditioning to keep it in the 0-5v range) and one of the hardware timers to very accuratley gauge the frequency
and why not use a alphanumeric led display to show the note, or even an lcd screen(quite cheap on ebay like 3$), then you can show the exact frequency and how far it is off, maybe even use the bottom row to show a line which would move left or right from center to show which way its off