We are living at a time now when the worlds of concert music and popular music have resumed their dialogue. Perhaps I have had a hand in this restoration myself, but certainly Kurt Weill began it long before I was born ... It seems that the wall between serious and popular music was erected primarily by Schoenberg and his followers. Since the late 1960s this wall has gradually crumbled and we are more or less back to the normal situation where concert musicians and popular musicians take a healthy interest in what their counterparts have done and are doing.One of the pieces on that album, 2X5, is so called because it is for an ensemble of two electric guitars, electric bass, piano and drums, mirrored by itself on a pre-recorded track. Sure sounds like a rock band, but the music itself is nothing like what a rock band would play:
One interesting bit: you may or may not know, but the guitar is notated on the treble clef even though it is more of a baritone instrument. It is a transposing instrument sounding an octave lower than written. Due to some odd glitch between his sampler and his notation program, Steve's score had the guitars an octave too high. When he showed it to guitarist Mark Stewart he just said, no problem, we will just use an octave transposer. Anyway, that's why the guitars sound so celestially high.
Let's go back to that idea of the two worlds of popular and classical being so distanced. Actually, there are three worlds in music: folk, popular and classical. The term "folk" is used to refer to all that music that is essentially the property and creation of a group or culture. This is what Bartók went around collecting in Bulgaria, Rumania, Turkey and so on. It is music without an individual composer and not done with much attention to commercial gain. A lot of so-called "world music" is folk music according to this definition. That would include Javanese gamelan music, but possibly not North Indian classical music.
Popular music is music that is produced by groups or individuals with an eye to commercial gain. This is not to say that some of it cannot be of high and lasting quality, but it is largely produced for immediate appreciation by widely-based audiences. There are degrees, of course. Jazz is at one end, being not so concerned with popular success, while the pop divas of the day, Rihanna, Beyoncé and so on, are at the other end. Classical, or as Steve Reich refers to it--serious or concert music--is music that is composed by individuals and written down to be performed in concert.
Everything else really derives from these fundamentals. If a popular musician becomes too esoteric he might either become a classical musician by default, or simply fade away. If a classical musician starts paying more attention to his popularity than his actual craft, then he or she may become a crossover musician on the way to being a popular musician. I suppose a new musicologist would accuse me of being too "essentialist" but so what? This is the truth of it: our fundamental motivations are significant in determining what the results are. An unpopular popular musician is one who failed to correctly judge the tastes of his audience. It doesn't make him a classical musician. A classical musician who will go to any lengths to amuse an audience is probably missing the mark as far as his music goes. And a folk musician who pays no attention to the traditions of his culture is probably not a very good folk musician, but may be a good popular musician.
Oddly enough, a lot of our problems in the classical music world these days come from people who are trying to help us out by showing young musicians how to "brand" themselves (sounds painful) or how orchestras should add video or mime or, who knows, smellovision, to jack up their audience numbers. The flip side of this might be a rock band writing a concerto for group and orchestra in order to gain prestige. Hey guys, don't bother? Steve Reich, the guy who really did bring down those walls didn't do it according to the methods that the marketing gurus recommend. Nope, he did it with just the music. And uncompromising music at that. The essence of the music contained something that had the potential to connect with popular music: a pulse. But there wasn't the slightest compromise with the basic fundamental principle of classical, concert, serious or art music: an individual sits down and composes something, writes it down in musical notation and arranges for it to be performed in concert.
Before the great onslaught of popular music in the 20th century, a lot of classical composers managed to be very popular without ceasing to be classical. I think this might be an option that is coming back.
But a dialogue between classical and popular musicians doesn't mean that they turn into one another. Quite the contrary.