The concept of pushing music from a music server to an Airport Express is pretty straight forward. Select the Express from within iTunes and music is sent via wired or wireless networks to the device. The express connects to an audio system via its digital or analog interface and that's it. As I mentioned in the opening paragraph this only allows one music selection to play throughout the network because the music server outputs its audio signal to the Express without any configuration possible. Using an AppleTV takes the basic push method of music streaming and adds the option to pull music using the AppleTV graphical user interface.
Using the AppleTV should be done with the unit connected to a television. I've done it blindly in the past and it's more trouble than it's worth. Once connected to a TV the visual display is almost identical to Apple's Front Row application. As detailed in the following video, the user can browse an entire collection of music, movies, photos, and even YouTube. This process may seem very basic for some readers, but the whole thing can be hard to grasp if one hasn't seen or used Front Row or an AppleTV before this time. When a user selects a song to play via the AppleTV the song is pulled from the main music server's library* to the AppleTV and output via HDMI or an Optical TosLink connection. At the same time an AppleTV in another location can be used in the same fashion to select a completely different song. In addition the main music server can go about its business unaffected by the two AppleTVs pulling music from its library. Thus three different music selections can be played fro the same source library using iTunes and AppleTVs. This can be expanded and Airport Express units can be interwoven with the network simultaneously. The whole solution is quite flexible.
*Synchronizing is also possible, but that's a topic for another article. For simplicity synchronizing will not be covered at this time. Synchronizing allows the main music server to be powered off. The configuration discussed in this article requires the main music server to be powered on for any music playback.
The last piece of the puzzle is remote control of the music playback for each location. This is equally as flexible. An iPod Touch or iPhone can be used to control each AppleTV from anywhere on the wireless network and to control the main music server. The free Apple Remote application works like a charm in this situation. The standard white Apple remote can also be used when within infrared sight of each AppleTV. The white remote navigates through the menu displayed on a television while the iPod Touch does not require any display.
A quick summary that may help newbies implement a wireless music distribution system.
1. Airport Express is one way. Music is pushed to the Airport Express from the main music server. All Airport Express units are either playing the same music as the main music server or they are "off."
2. AppleTV includes all the playback functions of the Airport Express plus, allows the user to pull music from the main music server independent of what the main music server is playing. AppleTV also has a great user interface navigable via television display.
The following diagram shows AppleTVs in a configuration with three independent zones / locations. Each of the three locations can play music and be controlled separately as long as the main music server is powered on. The video below is a simple demonstration of two zones selecting separate music simultaneously. It's fairly basic but provides a clear picture of the process.