Let's elaborate a little on the whole robot issue.
Let's say we do the same thing, but for Argerich. Scientists use sophisticated sensors and brain scans to monitor and record exactly every single burst of electricity in her body - all of the brain signals, all of the muscle signals. Then, using AI, they develop a program that acts exactly like the brain and nervous system of her body. Furthermore, they download this program into two separate robots - one that looks and moves exactly like Martha Argerich, and another which has no outer skin - in other words, you can see the metal parts. The scientists who do this of course tell no one (except Martha, because she's in on this little experiment.) The scientists then schedule two concerts in the same city a week apart. On one concert the look-alike Martha robot will play, and on another the plain robot will play. Despite the fact that both robots play exactly the same way, and futhermore the same way the real Martha plays, the reviews of the two nights are drastically different. Critics and the audience praise the concert with the real Martha - "She's done it again, folks!" - unbeknownst to the fact it is really a robot. However, the response to the 2nd concert is a bit different. People say - "Well, science has certainly made advances and it played the pieces technically perfect, but science can never duplicate "aht". Others say, "It just wasn't human, it's playing was lifeless." Of course the scientists are a bit confused, because other than external appearance, the two robots are exactly alike.
This little experiment illustrates the most basic human emotions. People are comfortable and happy with the familar - the robot that looked like Martha. But people become suspicious and distrustful of what they don't know or are unfamiliar with, often without good reason. This represents the response to the metal robot. This basic "fear of the unknown" has been one of the most powerful and influential forces in human history.
In the end, it is simply psychological. When people make music into "aht", they no longer think so much about the actual music - the sound waves in the air - but instead begin to think more about the performer and composer in metaphysical, philosophical ways. There is no physical difference between the robot Martha and the real Martha - thier music is EXACTLY the same in every way. Only the mind of a listener can warp and twist the sound and thier reaction to it in such a way as to create a difference between them.