Thanks, Rusty... been reading the code and thought that was the case, thanks for the confirmation.
Syd, that would be very easy... what you are going to do is average bands together. The build I did with TvOut uses 64 bands.. I just display all 64 bands (0-32kHz approximately, 500Hz/band). What you want is to reduce the number of bands, and that's done by averaging across the data. Since you want four bands out, that means you want to take the first 16 data points, add 'em together, and divide by 16. That's your value for band #1, which would be 0-8Khz. The next 16 data points are the second band, etc.
This will give you four values, to do with as you please. Since you are using simple on/off, do a bit of testing (or put four potentiometers on the Arduino's A1-A4) to set a threshhold value to switch the SSR's on (light up when sound in that band is above threshhold level), send that on/off (High/Low, 1/0) to four digital pins, hook up your SSR's to those pins. If you have them around, the Pots are probably the easiest way to set threshholds as real-world input levels (and desired response) change.
Working on an updated version of this, now that Turkey Day is past..