I read your point as being that microsecond scale changes in voltage (which you related to musical notes) would cause audible distortion. My point is that microsecond scale changes in voltage don't even exist in band limited audio, and especially not because a low note follows a high one, an event thousands of microseconds long at minimum.
I appreciate your point — and I actually agree with part of it.
We don’t have microsecond‑scale musical events. That part is clear.
My point was more about the electronics behavior. Even if the audio wave itself is slow, the electronics in the signal path deal with fast edges, charging/discharging of capacitances, and transient current demands due to how the eletronic circuits are built (capacitors, resistors, buffers, transistors, compensation networks, JFETs, attenuators, etc... this part I know well and I like to solder and repair equipment... as an old solder certifier in telecoms industry).
Any analog output stage (op‑amp, discrete, tube, whatever) has limits. When you get close to those limits, distortion increases — even if the audio signal itself is “slow.” Tubes are a great example, they are very slow by nature (compared to transistors), it rounds out the edges and makes the sound a bit softer. However side effect they have a tendency to introduce (good in some cases) distortion
You can attack my wording on these facts, and maybe semantics on tube behavior, but nothing here is factually incorrect I believe, at least from my experience.