A circuit which, when fed an input signal of a certain frequency, produces an output of exactly half that frequency, which is one octave lower. Octave dividers use a flip-flop circuit which changes its state on each leading (or trailing) edge of the input signal, which implies that the output takes the form of a square wave. A more general form of the circuit uses a counter, which counts the number of rising edges of the input signal and changes the state of the output each time a certain count is reached; such a circuit can divide the input frequency by any integer value (2, 3, 4, etc.) An octave divider can be used to, for example, add a reinforcing bass to a signal at a certain frequency. Octave dividers have also been used to generate all of the notes and frequencies on certain synthesizers, which is known as a divide-down architecture.