How to make an accurate metronome?

Hello,

I am creating a game based on rhythm  with Bolt, 

for my game I need a very precise metronome , my  attemp with bolt is not working propely because it is not precise at all , I think that this is due to the fact that the framerate is not a perfect 60fps, so the script rapidly desynchronize with the music ,

is there is a way to make this metronome precise ? 

here's my script