We all know the modern complaint: movie sound sucks now unless you have a high-end sound system. Frantically turning down the volume after turning it up to hear the dialogue only to need to turn it up again can be frustrating. Now, this doesn’t solve the underlying problem, but why not have a “Volume A” and “Volume B” you can easily set and toggle between with the simple press of a button?
You’re not wrong in any way but I would just like to clarify in the most friendly way that the use of spectrum in audio context is frequencies and not amplitude. Compressing the frequency spectrum is not really desired unless for in very particular applications like specialized lossy audio compression, which in turn is even more confusing the terminology because now compression is about reducing the data rate in a controlled degradation. Anyway, the proper terminology would be that the audio is dynamically compressed to a smaller range.