in physics last year we did some work with electric circuits,
including some lab work like building simple circuits, which spawned
this hair-brained scheme of mine.

We did some work with a component that I forgot the name of.  It
seemed to hold an amount of resistance (inversely? i forget)
proportional to the amount of sound present.  Since I don't know the
name of it, we'll call it an audio-resistor for clarity's sake.

i.e. (assuming the relationship is indeed inversely proportional) a
circuit that looks like:    positive terminal >> audio resistor >>
standard resistor >> LED >> Negative terminal    would light up
whenever you spoke into it, whereas if the relationship was
proportional, there would be some work doin ith transistors and
whatnot, and if you're interested in answering this question, you
don't need me to illustrate it.

My question is...  Im looking to build myself a mini-stage for my
drumkit.  I wanted to wire a yellow light to go on in the presence of
low-range, a red light to go on in the presence of mid-range, and a
blue light to go on in the presence of higher-frequencies.

This is based on the assumption that the make these "audio-resistors"
for different frequencies, and not just collective ambient sound.

I don't really need the wiring diagrams, although if you think ten
dollars is enough to write them out, go ahead, ill tip anyway.  I need
to know if this is possible, and where I would go about buying the
components...

Good Luck!!

P.S.  I would be building light-boxes consiting of 100watt flood
lights behind colored light gels ( i think they're called)

Hello sevennus, what you refer to is commonly called a "Color Organ".
It seems to be a popular lab project for science classes. There are
many kits and schematics available that will do exactly what you
require. Here are a few that I found:

http://www.aaroncake.net/circuits/organ.htm

Color Organ Schematic

http://www.a1parts.com/newkits/organ/

A1 COLOR ORGAN KIT

http://www.plaza101.com/plaza/search/res/r7235635.html

Velleman 3 Channel Color Organ Kit

This sound to light unit features three separate outputs which can be
controlled independently. Each output reacts to three different bands
of the musical spectrum: bass, midrange, and treble. Has built-in
microphone, so no connection is required to music source. Kit comes
complete with housing, knobs, and connectors. For use with
incandescent lamps only. Operating voltages: 110-125 or 220-240VAC
(50/60Hz). Max. load: 200W per channel (100W@110-125VAC). Net weight:
1-1/8 lbs.

http://www.hobbytron.net/9935.html

Power Blaster Color Organ Kit

I also came across this website that has lots of information
concerning color organs:

http://wolfstone.halloweenhost.com/TechBase/clobuy_CommercialColorOrgan.html

This should be a very interesting project and pretty impressive show
whem you get it set up onstage.

Rock on, Redhoss

exactly what I was looking for.