Cubism without Braque's beginning to morph into different art form (5)
I believe the answer is:
music
But I can't explain it at all! Could you help me understand?
(Other definitions for music that I've seen before include "Composer's product" , "Pleasant sound (to one's ears)" , "Melody, harmony" , "Art of instrumental performance" , "'''If ... be the food of love, play on'' (Twelfth Night) (5)'" .)