It seems the music_start and music_end events are misunderstood even by seasoned authors. I see many customs that put these before the music starts and after the song is completely silent. In the grand scheme of things it is no big deal but this is incorrect.
These are cues to the animation and audio systems to make the crowd applause and cheer.
Imagine you are at a concert and the band starts playing a song you love. Place [music_start] at THAT moment when a crowd would typically start clapping for a song AFTER they recognize the song. This will usually be after a couple of seconds, but occasionally it could be after an extended intro.
Now imaging you just enjoyed a great performance and the song is coming to an end. Place [music_end] at THAT moment when an audience would typically start to applause. This will usually be while the last notes of the song are still playing or a punctuated final note, but occasionally it will be during the silence of a poignant ending where the audience is hanging on every last note.