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The KarpluSynth synthesizer implements a 16-voice Karplus – Strong algorythm as shown in the diagram below. The input for typical Karplus – Strong sounds should consist of noise bursts, a burst of noise will be recirculating thru the feedback loop and create an average of a sample and a delayed copy of this sample. The delaytime is in this case linked to the perceived pitch.

There are 4 playmodes for the KarpluSynth;

• resyncing every single key – pluck mode
• resyncing every single key – bow mode
• sync once at first key – loop mode
• live audio input

To achieve the given example you should set the synth to pluck mode. While the synth doesn’t generate a burst of noise the loaded sample should do the trick. In bow mode the loaded sample is being looped but every single key pressed restarts a new instance of the sample. Bow and pluck mode refer to what the algorythm simulates, namely synthesising string sounds, while the sound will never come close to the real thing I strongly recommend you to play around with those two modes and to be creative with loading samples.

Loop mode (sync only at first key). In this mode only one instance of the loaded sample is used, the sample will start playing whenever a MIDI note is received by the KarpluSynth. Still 16 voices are available, this mode is very usefull for using e.g. drumloops or other rhythm oriented sounds. When using the extra feature beat mode, the application shows the BPM of the loaded soundfile (supposing that the file consists of two measures, each containing 4 beats, you can set the beat division to recalculate the BPM). But to make things even more interesting you can set the BPM as well, which will change the playback speed of the sample, usually this will lead to a pitch difference but while in the algorythm the delay is mostly responsible for the pitch it doesn’t really affect the preceived pitch and therefor it is mainly used for slowing down or speeding up your sounds.

Live input mode, which is quite tricky cause we are already dealing with feedback loops within the application… With voice input it kind of sounds like a cheap vocoder.

Also a loop can be selected within the supplied sample, just click/drag over the sample-display, and most probably now you can figure out when the select all button comes in handy.

Installation notes…
Installing the KarpluSynth is very easy, after you have mounted the Disk Image you can just drag the folder called KarpluSynth to any location on your hard drive. To get up and running simply double-click KarpluSynth, load a soundfile (supported files : *.wav, *.au, *.aiff) and probably you are ready right now. The settings window gives you control over MIDI input, routing controller data to the 4 main sliders and the audio driver.

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http://student-kmt.hku.nl/~leo/ (409 clicks)

filed under the Max/MSP category.