Wrong. I'm talking about the AA being the media server vs. the remote device.
What I read sounded more like someone asking how it worked when you have your music on your iphone and had the AA play that music. Then it is not really being the music server but is acting as a remote device. The AA can be a whole load of things at once.
I have a Synology NAS that all my music is sitting on. I can listen to that music on my tables using the DSaudio app that will connect to the Synology that has all the music and catalog that you can select the tunes. As you add them to the play list they will queue up the song and just before the song is about to play the software will download a copy of that song to the local tablet storage so that the copy is local. You can control the cache size so that it will buffer about 100-1000 songs. If I ask it to play a song that it has already buffered then it doesn't need to redownload the song and can play from the local copy.
Now my Pioneer stereo can play DLNA and AirPlay too. But it has a very small buffer inside. Not even enough to play a large song so it I queued up say the 2112 by rush and after listening for a minute, turned off my tablet (off, not standby), then the song will continue to play for about 4-5 minutes then stop as it will run out of song data. Effectively the receiver is not playing streamed music in real time, but buffering and playing from the buffer. it just doesn't have enough buffer space to grab the whole song like my tablet can (and like the AA can) and the receiver also doesn't do song management so if you have a play list with the same song playing 5 times in a row it will re-buffer the song each time.
