The new era of music combines aspects of past vanguards and places them on a tightrope two hundred feet up in the air. The balancing stick measures what styles are employed by the tightrope walker. Careful! One measure more than the other might set the composer off balance, to lose her footing and fall helplessly, arms flailing, to the ground where a thousand curious spectators stand and sketch impressions.
If I made a list of the ten most important things a composer could learn from, watching all Tarkovsky films would be on the list. Of this particular shot, the 1:58 mark is my favourite. But really, the whole scene is incredible.