I'm attempting to make a spectrum equaliser
Following the instructions in the thread on sparkfun, I've tried samping fast for 50ms, and then using the difference between the max and min, but this value seems pretty random.
and connected 3.3v to AREF
If you're using an external reference on the AREF pin, you must set the analog reference to EXTERNAL before calling analogRead(). Otherwise, you will short together the active reference voltage (internally generated) and the AREF pin, possibly damaging the microcontroller on your Arduino board.