We are thinking actually considering putting a speaker system into our garden to enhance the summer evenings with some music. Having looked into this there are lots of ways of doing it, the old way was with speaker cable running to a speaker that was in the garden and usually it was quite expensive because it had to stand up to the British weather. Therefore the speaker had to be weatherproof and the cable running to the speaker also had to be weatherproof otherwise once it got wet through snow or rain it would be useless.
But today we have wireless speakers that can be transported with you and can take music from iTunes via Bluetooth or airplay and the speakers are very powerful and often you only need one to ride excellent music either background or foreground.
So really the task now is to work out what kind of speakers we would like and bearing in mind how we would feed those speakers with music, we are probably use iTunes as it makes sense because you are Music is there. But having said that there are several apps but also supply music like Spotify. which makes sense if you have the right bandwidth to handle Spotify because it clearly runs across the Internet and if you have other applications or other people downloading are using wireless then Spotify is affected often in a bad way which would ruin the clarity of the music and therefore the ambience.
So I think a wireless or Bluetooth speaker makes sense being fed by a device potentially your phone with music on and it seems to be the simplest way to do this and there is no need for big device is lots of cables these days.