Nice little game! I liked the art and music; theremin is perfect to do the ghosty notes!
I stopped at 111 points. Once I got that the ghosts always spawn at the same place, at the same pace, it became impossible for me to lose. To balance this, I suggest you make them spawn randomly along the side of the screen but not as often as they do now and make the game go slower so it's not too hard.
Also, sometimes I thought I missed a ghost because their death animation is so close to the normal one. Maybe making them stop moving or adding a slash would have made this a little bit more obvious!