The rule of three applies to so many things in the creative arts: from stage plays, screenplays, sitcom scripts, musical concertos, photo composition, landscape paintings, lectures and speeches, to even joke telling constructs. In stripped down song accompaniments we have the three chord trick of course (tonic, dominant and sub-dominant chords). In artworks though, check out the Divine Section (Fibanacci Principle) where the use of threes explains a lot.