Free, so how do you think speakers work when you get a phone call and recognize the voice, or vice versa? :) It would be pretty weird if there were vocal chords in your cell phone. Maybe you’d have to feed it to keep it working. The device in your phone is a speaker too.
I think you are overthinking it a little bit. If all that was recorded in a recording was the notes, like sheet music, then it would be impossible to replay a specific performance. What’s being recorded (as much as possible) is the individual vibrations that make up a sound. For instance, on a violin middle C is played. The CD/MP3 whatever doesn’t record middle C. The microphone recorded the fundamental and all the overtones produced by that specific instrument at that point in time, including any studio sounds, the sound of the bow pulling across the string, the vibrations of the body as well as any air moving through the holes on the top. There's also the effect of the bridge, and a little finger's worth of wood placed int he body of the violin to give it more complexity. A microphone should capture as much of that as possible, much like your ears do.
The speaker driver itself should be like a blank page, or like a projection screen. Without any image of it’s own, it should reflect only what is cast upon it. No driver is actually like this, and no driver is perfect, but that is what makers strive for.
Any driver, regardless of material, tries to function like a pure piston and NOT like a musical instrument. That piston should move back and forth exactly as the input voltage asks of it. It should not "ring" or cast on any overtones of it’s own, like a piano or violin always must do. It is in essence a microphone in reverse.
Best,
Erik
