This was my first attempt at reading music and I did it using the direct output to the speaker. The method was not great but now I actually have a nice chip that pulls 7 bands of detail using 2 digital and 1 analog pin.
This chip...
http://www.bliptronics.com/item.aspx?ItemID=111
Plus this adapter ..
http://www.proto-advantage.com/store/product_info.php?products_id=2200001
Plus these .33pf capacitors (along with other radio shack partsA).
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320517060962&ssPageName=STRK:MEWNX:IT
I was able to put together a pretty nice board using this .. on breadboard first and then an easy solder job (the SMD chip to the adapter being the most challenging but is still SMD 101).
If you already have components to read the music, let me know what you are using and what you have for start code (something that can make one light dim/brighten with amplitude) and I can provide some assistance on how to get that and turn it into something cooler 
Hope that helps get you started.