It could very well be between a metaphor and idiom.... An idiom would be something like a dark horse- could be taken literally or figuratively... A metaphor makes a comparison of some sort or something along those line, it seems more of a metaphor because it could be comparing the wait to the music that used to be heard in the community during childhood. (I hope this helps and again that's just the thing that comes to mind for me- I could be wrong)
