i can give u some hints for deafeating the dark guitar maniac:
1st when dark guitar maniac uses his move (Mischeif) some small dark guitar maniacs appear on the guitar board dont get tricked some hide Keys or some would appear as fake keys which they will lift up and dissappear 2nd understand that dont look at dark guitar maniac he will just trick u... 3rd after u win against dark guitar maniac u will get a megabat guitar!!! congratz!!
u can change quality before starting a song by pressing the Q button set it to low to avoid lag and if u dont want the sounds like Good! Godly! bla bla click on toggle voice once.. Hope that helped :D