The horizontal Crescendo is a really good footsies tool, since it whiff punishes tons of stuff from surprising ranges. The vertical Crescendo in the air can be used to fake movement (sort of like a dive kick) and also used for tricky crossups, although Aria doesn’t need to use Crescendo to do crossup stuff in booster body. Shadow crescendo has a hit of armor so it can be used as a situational reversal, while the heavy one on the ground is truly invincible but they have to be pretty close to hit. Another pretty common use of it is the medium version in the air. You can fly around and punish things on reaction, or bait anti-airs and then punish with it.