And in music (setting copyright laws and royalty issues aside), borrowing a sound, a style, a sequence of notes, or an entire tune is such an ancient and well-established tradition (everywhere, i think) that it's hard to think of it as anything but part of the tradition of music itself.
In folk music, they used to call it "the folk process," and I kind of like that name.
If madness made us strong, we would all be invincible.