Unfortunately the two shields don't seem to be compatible:
The audio spectrum analyzer shield uses pins 4 an 5 for triggering and reset as well as A0 and A1 for getting the values.
The wave shield seems to use pins 4 and 5 too according to the shield list:
http://shieldlist.org/adafruit/wave
One possibility is an go-between shield (http://www.sparkfun.com/products/11002) which is able to physically remap pins to other pins.