That positive and negative stands for the connection to the "music" , and then the side channel connects to the speaker.
Maybe it doesnt work unless u run on it a timer, but I was wondering if you made the LC oscillator run at 10x the maximum frequency of the music, maybe it could be continuous?
But it would have to be a little capacitor, it is an amplification only for very quiet signals, but I wonder if you have a heap in parallel - then that could make it loud.