Nowadays it seems to be all about the sound distorting from one thing into another. Instruments are not exactly defined things, but effects instead are gradually filtered, layered, and mixed into something new as a song progresses.
The future of pop music nowadays is the most random variety of both recognizable, obscure, and provocative sound clips.
Rhythm I believe is the backbone of all music, and always will be. It drives the mysterious randomness as a song is introduced, as well as the resolution. Repetition returns everything into the grand rhythm loop again, and makes a song predictable in a way people seem to like.
Thanks for sharing @mobbs.
Though there are many examples of music without rhythm, such as this infamous piece:
in terms of pop music, I can't imagine a success without a predictable, repeating pattern. I'd love to see someone try and get rhythmless music popular though =DYeah, I was thinking about soundtracks and background music for tv and theater. It is a very different set of rules for music made to aid a visual story being told in the same parallel moment, vs. music being performed solely for musical entertainment.