Editing Karplus–Strong string synthesis (section)

== How it works ==
[[File:Karplus-strong-schematic.svg|center]]


# A short excitation waveform (of length L samples) is generated. In the original algorithm, this was a burst of [[white noise]], but it can also include any [[wideband]] signal, such as a rapid [[sine wave]] [[chirp]] or frequency sweep, or a single cycle of a [[sawtooth wave]] or [[Square wave (waveform)|square wave]].
# This excitation is output and simultaneously fed back into a [[Analog delay line|delay line]] L samples long.
# The output of the delay line is fed through a [[audio filter|filter]].  The [[Gain (electronics)|gain]] of the filter must be less than 1 at all frequencies, to maintain a stable [[positive feedback]] loop. The filter can be a first-order lowpass filter (as pictured).  In the original algorithm, the filter consisted of averaging two adjacent samples, a particularly simple filter that can be implemented without a multiplier, requiring only shift and add operations. The filter characteristics are crucial in determining the harmonic structure of the decaying tone.
# The filtered output is simultaneously mixed into the output and fed back into the delay line.