Examine what Bingle Bog signifies in human world.
The original question had to be edited down. Bingle Bog represents any modern state of musical appreciation. The bog is a realm where there is one voice. The frog's voice is what provides majority of the musical "entertainment" for the animals. The frog has a fairly good control of the musical marketplace. This is where the bog represents any area in which music is appreciated.
The fundamental threat that the nightingale displays is that her song is perceived as more musically superior to the frog's. It is in this exercise of power and control that the frog seeks to silence the bird's voice in the bog. The bog is that musical realm in which individuals seek to maintain their control. It is in this realm where music is not seen as an end in its own right. Rather, it is seen as a means to an end. Music is seen as a means to deliver control for another. This is how the frog sees it and it is for this reason that the frog "trains" the nightingale so well that she dies. The bog goes back to the way things were prior to the bird's arrival. The frog has resumed his control of the musical arena in the bog. The bog is that realm of music meant for public appreciation, yet one in which people use music as a means to their own end of control or power.