No, analog frequency is theoretically simple - just mix it with a sinewave and you'll create a new frequency spectrum; e.g. if y is the input frequency & x is the mix freq, you get 2 resulting frequencies: x+y & x-y (due to the trig identity: sin(x)sin(y) = 0.5(cos(x-y)-cos(x+y)) ). The problem is that to make it useful, you have to filter out the unwanted frequencies from the initial spectrum before mixing, and you may need to filter again after the mixer. The mixer can be a simple squarewave mixer (will introduce odd harmonics though) using a 555, an inverting amp and a analog MUX selecting between the inverted and noninverted signal at the rate of the mixing frequency.
You could also just sample the signal at some rate using an analog switch and an oscillator - this will create aliasing which will fold the frequency spectrum; the input signal must be filtered before sampling though, so that only the frequencies of interest are folded.
You can alternately use a peak-detector on the bands, which will remove the high frequencies and give you a signal that is the envelope of the peaks in the old signal - not frequency shifting, I know, but you'll get a low frequency signal that the woofer can handle, and it will be based on the mid or high spectrum, which may give you passable result for you light show.