Eventide

The harmoniser can be as simple as adding one note an octave above or below as in the octaver through to adding the major or minor third and beyond.

Multi effects units combine all the common effects and some uncommon ones into one box usually with a range of switches allowing you for example to create different patches allowing you to go from a clean sound with chorus straight into a high gain lead patch with delay with the press of a button. Infinite sounds in a compact package, the swiss army knife of guitar effects.