Music knows no walls. It travels from apartment to apartment, welcome or not; it shakes the bedrooms of the parents of teenagers; it spills, boomingly, from passing SUVs onto previously silent sidewalks. And there are other boundaries that music penetrates, those that can't be seen: the barricades of tradition and technology.
As one band sang, "This is the game that moves as you play." Even as one barrier is defeated, another goes up. File-sharing services allow a river of music to flow across your desktop--though lawsuits may slow the flood to a trickle. The practice of sampling that lies at the...