What’s the purpose of the “Songbird Defense System” statues

bioshock-infinite

In Bioshock Infinite, there is a Comstock statue in her room, that starts playing a tune, and makes Elizabeth realize Songbird is coming back– we also see these statues later in the game, sometimes they play a tune, sometimes they don't.

What are they? Why were they built? What makes them play their tunes? I don't think the game ever fully fleshed this out, unless I missed something..

Best Answer

The tune summons and controls the songbird. This is established near the end. Why they're all over the island rather than just in Elizabeth's tower- good planning on Comstock's part, I guess?