Music Theory for (Non)Musicians and (Non)Programmers
Random Thoughts, Part One
Can a computer make music?
I'll go against the grain here and say "yes" while splicing words. If by "make," one means "compose", then I do believe that is possible, up to a point. If one means "play," then I don't think so, but perhaps this could be an interesting research project for those who are better at this stuff than I am. I'm only going to explain what I think from the perspective of an okay composer and musician. This article is more philosophical than technical, though if you are technical, this article may give you some food for thought..
What is a composition?
A composition is merely arranging notes in a way that makes sense to the composer. Notice I didn't say "within the rules of music theory" and I did not say "makes sense to the listener." Stating "within the rules of music theory" suggests that there is a mechanical and unbending "way" to compose music, which is not always true. Music doesn't have to make sense to the listener; one cannot include "all listeners" in this statement because no one song is liked by all listeners and no listener likes all songs.
Take, for example, a blues player. Her composition will be broken down into the usual structures found in blues music. Whether you love or hate the blues, the music is considered more "accessible" than 4'33 by John Cage , and no one can argue, whether they enjoy it or not, that 4'33 doesn't break all rules of music theory, as that is the entire point of the piece.
In an earlier article, we briefly explored the "three chords of Rock & Roll" and it doesn't take much imagination how easy it is for a computer to generate such songs.
What about more complex and beautiful pieces, such as Ravel's Left Handed Concerto?  Can a computer compose something like this, while considering the limitations one can do with only one hand? Perhaps, but I wouldn't know.
Simplifying all of this, I think it is possible for a computer to compose, as long as we define "composition" as the tying together of notes in a "logical" sequence. How logical would be limited by the abilities of the programs underlying the computer, just as a composition of a human is limited by his or her abilities.
My own composition are considered fairly complex, depending on who is listening to it, but the music itself follows a fairly simplistic expression of music theory. There isn't a whole lot of flair, off-key notes, or anything that is too "difficult" for a decent guitarist to master.
Can a Computer Play Music?
This, I mostly disagree with. Now, one can argue that a dance track is a computer playing music, but here, I must disagree. Dance is different because it is composed by a musician, who happens to compose music through the use of digital equipment. Of course, if a computer can compose dance music and do it well, then it seems a simple logical extension that a computer can play this music.
But the question isn't really about techno music. The question is whether a computer can convincingly play a violin, an instrument that is a struggle for even humans to play well. I won't venture to answer this question with a "yes" or "no." Instead, I'll explore what I feel are the needed components to play music well and convincingly. I'll let you come up with your own answer.
I believe the primary component of music, played live, is the tensity between perfect and not-perfect. This is not to be confused with the expression "she played it perfectly." When that expression is used, the speaker is attempting to say that the music sounded good, whether that is because she played with emotion, technical accuracy, or a some other parameter that can't be explained fully.
When I mean "mistake," I mean mean making real mistakes, like hitting a bumb note, not playing in perfect time, holding a note too long, etc. No musician can play with metronome precision, even with a metronome. A listener who does hear a musician play with near metronome precision may say "She plays like a robot." Good music is somewhere between perfect robotic play (as a computer will do) and totally screwing up.
Mistakes tie into playing music in general, and it is, in my opinion, the secret sauce of composing good and interesting music. If "to err is to be being human," the arts gain their humanity through the errors made through creation, learning, and playing live. Just as few songs were created on a weekend, no good musician attains mastery without tons of mistakes along the way. The culmination of these mistakes makes a musician what she is, and how she dissolves these mistakes while playing is the critical difference between her and her five years hence.
The strike is the moment when the musician first pushes, blows, or hits a note on her instrument. This strike is actually a bit off-key, a touch sharper than the note she is striking. The note itself is a nanosecond after the strike, so a note isn't actually "C" all the way through. It may begin slightly sharp, sustain "C" for a moment, then taper off to lower notes, until it is no longer heard. Anyone who has tuned or intoned their instrument will know that you measure the note during the sustain moment, as opposed to the strike.
The strike, how the musician strikes, and how she recovers from the strike and flow into the sustain, is an essential element of her play. Perfecting the strike is a combination of learning how to play quickly, with confidence, and learning how to listen to herself play, along with figuring out what sounds good to her after years of making mistakes.
No good musician can be good without a sense of tempo and beat, but no musician is playing in perfect beat, even while backed by an orchestra or a drummer. They are close to metronome perfection, but each beat is going to drift a nanosecond early or late. The better a musician is, the less obvious this drifting in beats is, but it is still there. We, the listeners, know it is happening although we aren't exactly aware of it, but it is a component of not playing robotic. Josef Hoffman, among others, suggests practicing little with a metronome, only to cover mechanics, but to turn it off after a few minutes.
Spontaneity and Growth
You can call spontaneity improvisation, or, if you view the creative arts as I do, working around mistakes. However, there is a level of play that goes beyond mistakes. This is adding a little "color" to the music, such as adding a bend where notes are generally smooth, adding a gracenote, or suggesting a pause in a high tempo part of the piece. Knowing when and how to move beyond the music, as written, can be viewed as a slight reinterpretation, and to be sure, the very expression, begat from the musician's comfort with her instrument, along with years of experience, will shift the song into areas that it was not found before. Grab any piece of music you like, and it isn't hard to notice the mechanical technique a "child prodigy" handles the music compared to a musician in her 60s. This isn't restricted to any genre of music. You can find almost any hit from years ago and hear the difference in technique and style when played live today. Spontaneity goes hand in hand with growth, which, in turn, goes hand in hand with "taste."
A part of being a musician is watching yourself grow, but this is not limited to your own self. Other musicians grow as well, and this connection, no matter how vacuous, is critical to the human connection we have with the musician. There is nothing more exciting than seeing a musician start at the bottom and slowly claw her way to a decent performer. A band that lasts for years doesn't make themselves last through the iron will of a prolific discography, but through their ability to constantly surprise their fans. If every album brings something new to the table, if the way a concert played today is different than the concert played 10 years ago, then the band has grown, and has earned more time in the long history of music. It would be incredibly disappointing to see a band, all in their 50s, play in the exact same style and naivety they played in their 20s.
 Ira Glass on Storytelling, part 1 of 4 (Although this is about story-telling, I think what Ira discusses in this series is relevant to music.)