Variety, contrast, change. The liveliness of music is bound up with dynamism. La Monte Young is fond of saying that "contrast is for those who can't compose", but with all due respect to my teacher, contrast is essential — Young's own music is full of contrast — and the critical issue for composers is management of contrast, within the scale and scope of a given musical environment. To my ears, there is more dynamic variety within much Q'in or clavichord music — instruments which can never rise above the dynamic level of piano — than is available on the best made and played Steinway. The absolute range of dynamic contrast may be smaller, but the degree of differentiation, the scaling within that range, is much greater by being much more refined.* Even the most disciplined performance of Young's Any Integer (for Henry Flynt), a piece in which a single piano cluster is repeated as precisely as possible for a number (often a large number) of time soon becomes totally engaging through the discovery of the smallest possible variations.
Variety, contrast, and change can come from within or without. The most familiar childrens' kaleidoscope reflects colored stones or pieces of glass or plastic or paper onto parallel mirrors sharing a viewing tube with the objects. The relative positions of the objects can be changed by moving them within their chamber, sometimes by shaking, sometimes by turning, but the total range of available shapes and colors is contained. But there is also the teleidoscope, a variation on the kaleidoscope, in which, instead of objects contained within the tube, has a lens and an open view, allowing the internal mirrors to reflect images from outside. It might be useful to think of contrast in music functioning with a similar distinction.