Really nice audio design! I was a little confused at times how I was supposed to be using the instruments, but it looks and sounds lovely! My game also froze on a level and I had to restart.
Thanks for playing! And don't worry, my girlfriend also said there were harder puzzles haha ;0 Regarding the bug, is it level 6 ? It seems to be problematic for others too? May I also ask what browser you are using?