Fun fact: The diaphragm is a muscle...that attaches to your lumbar vertebra. Remember what's happening to your spine when you're wearing heels? You're changing the shape of your spine, which affects your diaphragm. If your spinal curves are changing in response to your shoes, your diaphragm's capacity for full expansion is probably affected. (You could also already have a hypertonic diaphragm, meaning super tight, which is also not good.) Why would you want to intentionally shorten your capacity for a full and supported breath under pressure when you're musical instrument depends on it? I don't know. (Singers, I'm talking to YOU too!) Not only that, but your body will go to the more shallow area of respiration, or that upper chest/hyperventilation breath, which is not good for anybody, regardless of instrument, under pressure.
Scenario 2: You're a string player, and you only wear heels for solo concerts.
First of all, glad you don't wear them all the time. However, let's think about this practically. If you practice barefooted/flat shoes on your repertoire, finding a place of neutral axial extension (good posture), neutral pelvic tilt, and good foot position (topic for another day), why are you going to throw that into limbo in a concert, when you're under pressure? Or even worse, at an audition??? Perhaps you're not as into the whole "grounding" thing as I am, but your feet are your foundation when you're nervous, and your knees definitely shake more in heels. (Or mine do.) So why change another factor of anxiety and performance when you could have something absolutely consistent and secure to base your body on? I don't know.
Scenario 3: You're a pianist, and you wear heels regularly.
I'm not a very good pianist, but I do know you need access to your pedals and your ankles/calves, in order to point and flex the feet. (Plantar flexion and dorsiflexion). We already know that heels limit your ankle flexibility and shorten your calves, so over time, that whole area with begin to shorten and lose range of motion. Yikes! That doesn't sound good. There have been some studies on how habitual wear affects long term R.O.M., so beware!
If you can't drive in the shoes you're wearing, you probably shouldn't walk, perform, or stand in them.
It doesn't mean that you can't wear fun shoes sometimes...it just means that you should wear them sparingly, and not in stressful performance situations. Help your diaphragm, your feet, and your general stress level by saving the heels for a non-performance situation.