The Greek “techné” translates both “art” and “craft.” Plato did not recognize any difference between what we call the arts and the crafts or trades. He did not use any equivalent to our concept of “fine art,” according to which such art is essentially removed from practical life and is reserved for some special realm of rarefied, non-worldly experience. All art is practical, on the Platonic view, since, as any techné, it tends to the goodness of human life. Plato did, of course, talk about counterfeit art, art of the sort that appeals to and cultivates the selfish fantasy life of its audience and that thereby diminishes their ability to function as friends and as citizens. Such counterfeit art is not like what we call fine art, but more like what we would call “the movies;” it’s essentially cynical manipulation of popular images for the sake of monetary profit.
Both the musician and the doctor are, as masters of technés, artists, on Plato’s view. Both of them bring theoretical knowledge to practice for the sake of the good. In the case of the doctor, that good is the health of the patient; in the case of the musician, that good is the beauty of the music. The “intoxication” of a great piece of music is, I would say, “divine madness.”[1]
Especially in the Phaedrus, Socrates describes the perception of reality (which is the function of “reason”) as a joyful experience. Platonic rationality is not, then, mental coolness, and Platonic self-control is not repression of emotion. When a symphony orchestra plays well, there is a sense in which the orchestra is now “in control.” That’s the control of Platonic self-control. There is another, more pejorative sense of “control” as willful and repressive. If the orchestra tries to control the music in this latter sense of ‘control’, it kills the spirit of the music.
Look at it this way: The good kind of control is one in which, as it were, the music controls the orchestra; the orchestra submits to the authority of the music and lets it take over. This submission or surrender requires a good deal of musical wisdom; a bad musician does not have the ability to surrender his will in this way. Plato’s idea of reason can be characterized as submission of this sort to reality.
[1] See the Phaedrus. inspired by its beauty. The opposition that we tend to ascribe to “reason” and “emotion” is not found anywhere in the Platonic dialogues. I believe that this concept of reason is derived primarily from the 17th century European Enlightenment that identified rationality with the spirit of a mechanical physical science. This concept set up a series of oppositions between reason and emotion, thinking and feeling, reflection and sensation, etc. that Plato would not have countenanced.