One of the many tricks guitarists have up their collective sleeves is called a sub-octave generator. Although it may be suitable for any genre of music, a sub-octave pedal is particularly effective when used to make heavy metal music sound, well, heavier! Overuse of a sub-octave generator can result in an overly muddy sound, but by dialing in just enough of the effect, shredders can achieve a thicker, more aggressive tone that's perfect for heavy metal. The sound can also help to fatten up the sound of a 3-piece power trio. Some processors can also produce a second signal that's an octave up, so tyou can actually sound like three guitars playing at once!