Pitch shifting pedals either raise or lower (or sometimes both) a pitch by a specified interval. The most simple type of pitch shifting effect is an octave pedal (such as a Boss Octaver) that will produce notes either one or two octaves below the original note (or a blend of the two). More sophisticated pitch shifting pedals, also called harmonizers, can create diatonic harmony with the original note, providing two or more notes in addition to the original. The much celebrated Digitech Whammy pedal can provide such effects and also shift them in real time using the onboard foot controller. Everyone from Steve Vai to Tom Morello has used pitch shifting effects at one time or another.