A canon, in Bach's own hand.
Not to be confused with the ABC radio show of the same name.
For years listening to music, my first love and probably what I'm best at, something has always gone straight to the core of my being. A particular type of music, or technique, although that's an ugly word for this. And it's taken me a long time to find the word for this specific deep existential jucies flowing thing.
It's counterpoint. Also sometimes called contrapuntal music. Any dicitionary definition will do, this one from Answers.com fits the bill:
The technique of combining two or more melodic lines in such a way that they establish a harmonic relationship while retaining their linear individuality.
[Before going on, it's interesting that the ABC radio show of the same name was created to 'counter' the perception that the ABC is a hotbed of socialist propaganda. So they botched that as a program title, because it doesn't mean that at all.]
Counterpoint done well is, for me, the highest form of musical art, and maybe of any art. Bach (JS) explored it with admirable German efficiency, but to defend the Germans, despite their reputation for obsessive mechanical efficiency, in music they've produced some of the most beautiful things in all of history. Bach's work with canons and fugues and his Art of Fugue were an exhaustive examination of all of the possibilities of counterpoint, which can make it sound a little busy to the unwary ear. But once you realise what's going on and the ear adjusts, it's a profusion of beauty.
Counterpoint is sublime because it reconciles the two sides of modern Western music - melody and harmony. It's melody that makes a harmony with another melody, and you can multiply the number of melodies and therefore number of harmonies as long as you like. It's not the usual thing of a melody accompanied by harmonies, but rather what you get when melodies create their own harmonies and harmonies their own melodies. It's the music you get when order (harmony) and disorder (melody) continuously feed off each other in a constantly renewed poise.
When you hear counterpoint done well, it can fill you with spontaneous joy, and you can sometimes see musicians accidentally stumble upon a contrapuntal line, which then animates their entire body with a look of delight. Sometimes it's more enjoyable when not quite as thorough as Bach, jumping out of you unexpectedly all over the place from within a standard song form. The best exponent of this I've heard is Branford Marsalis, part of the famous jazz family. Sting hired him to play saxophone back in the 1980s, and if you listen to the Dream of the Blue Turtles album (but much better again, the live album and also video of the project), you'll hear counterpoint of exquisite subtlety and humour (and there's something intrinsically humorous about all counterpoint).
Fire up YouTube and search for one of the duets Marsalis has performed with Sting on Roxanne. Marsalis darts in and out of the main melody with prodigiously inventive contrapuntal lines, constructing counter-melody after counter-melody, which harmonise with the main melody and with each other.
You can think of counterpoint outside art, it's really just any play of order and disorder, where every disorder is really the emergence of another order, and any order is continuously being unravelled even as it emerges in favour of new orders. It's the denial of order and disorder as categories, the living expression of their mutual relationship. The poised play of light and dark, lightness and heaviness, clarity and confusion. No either/or of dualistic sentimentalism, with climactic peaks and bottomless depths of despair. No false unity or wholeness either. A poised, creative play which flirts with all of those false absolutes.
Marsalis showing how its done.