This is how I do whole house audio.
Parts list:
1- Harman/Kardon HK3390 Stereo Receiver
4 pr.- InwallTech HD650W
1- InwallTech SS4R Speaker Selector
1- Apple Airport Express
1- Computer running iTunes connected to the house network or having Wifi
It all starts at your computer with the iTunes program. All your music gets downloaded onto your computer either physically with your CD’s or via downloading through iTunes or some other form of digital download.
From this iTunes interface you then basically broadcast your own radio station (what’s playing on iTunes) to your new Airport Express. You can pick which speakers to play to within iTunes. (You can click on the image to see it larger:

iTunes showing speakers to play to
When you click on that area in the lower right, you get this dialogue:

Volume levels for multiple speakers
If you want to play just to your computer speakers, you can pick just them. If you want both, you can pick both. If you want to send it to your Airport Express, you can pick just that. If you have MORE THAN ONE Airport Express, you can select ALL of them or ANY combination. This takes it one step further in that you can now WIRELESSLY send your music to more than one receiver. Maybe you have two levels and can’t get a speaker wire (or don’t care to go to that effort) to the second floor.
Your new Airport Express has a 1/8″ headphone jack that you plug into your receiver.

Airport Express with Y-Adaptor for Music
Then into back of receiver with the other end of the Y-Adaptor

RCA Jack end of Y-Adaptor
From here you then have your whole house audio system plug into your receiver, then to the speaker selector, then to optional volume controls and onto the speakers. Here’s a link to a 4-Room Whole House Kit like I have operating (except with ceiling speakers, mine is a cathedral ceiling that I chose to put rectangle(wall style) inwalls).

Kitchen Speakers InwallTech HD-650W
Now use your iPad, iTouch or iPhone, walk around the house and change the track, search your whole library, change the volume or whatever!

iPad with "Remote" app

iPad with "Remote" app