A dissonance from "accidental" measures, rather than via premeditated notes on staff paper or in jazz improv. In hip-hop it's samples that sound incongruous to the key of the music - the rogue horn hit in Full Force's "Alice" or the "annoying" high-pitched samples of early Public Enemy (and their general sonic gumbo as well). In rock, Thurston Moore's unusual tunings begat nice dissonances between Sonic Youth's guitars, opening up a unique harmonic world. Or Christian Marclay's turntablisms.