This is a music-related rebus puzzle, for the fortnight challenge of mixing unconventional tags, hence this music rebus.
What famous quote from a movie is suggested in the above rebus?
In the first measure, ALL of the notes on the piano are to be played simultaneously. In the second measure, six Bs are to be played. The third measure is the first bar of J.S. Bach's Prelude in C from Book 1 of the Well-Tempered Clavier.
ALL B BACH
This, of course, is in reference to 'I'll Be Back' from The Terminator.