Component
Plucked string
v0.5.108
Oscillators & voicesPhysical model
A plucked string (Karplus-Strong).
Software v0.5.108
Overview
A plucked string (Karplus-Strong).
A plucked string using Karplus-Strong synthesis. Each rising edge on Gate plucks the string again at the pitch on V/Oct; the note then dies away on its own, high harmonics first, as on a real string.
Pluck sets how hard the string is plucked, from 0.01 to 1. Pluck and Level both have a CV input, so an envelope or a random source can vary the touch from note to note. It is one voice per module.
Controls
| Control | Range | Default | What it does |
|---|---|---|---|
| Pluck | 0.01 … 1 | 0.8 | The pluck: low = dull, high = bright. |
| Level | 0 … 1 | 0.8 | Output volume. |
Ports
| Port | Direction | Signal | What it carries |
|---|---|---|---|
| V/Oct | in | cv | Pitch, 1 V per octave; read at the pluck. |
| Gate | in | gate | Each rising edge plucks the string. |
| P+ | in | cv | CV for Pluck. |
| L+ | in | cv | CV for Level. |
| Out | out | audio | Mono audio output. |
How it works
Karplus-Strong is the classic short delay-line model of a string. A burst of noise (the pluck, scaled by Pluck) is fed into a delay line whose length sets the pitch. The output is fed back through an averaging filter (a factor of 32686/65536), which takes the high harmonics away faster than the low ones and gives the natural plucked decay. The delay line is at most 536 samples long, so the lowest note is about 82 Hz. An amplifier after the string sets the output level.
The firmware uses AudioSynthKarplusStrong from the Teensy Audio Library.
The browser simulator runs a line-for-line copy of the same integer
arithmetic, in Teensy blocks of 128 samples, so a pluck waits for the next
block just as on the hardware.
Runs on
- Teensy 4.1 (the MusicBrain Brain): about 0.3 % CPU per instance (one note, default settings), measured on firmware 0.5.108.
- The browser: the editor's simulator runs the same C++ code as WebAssembly, so what you hear while patching is what the Brain plays.
Try it
In the editor's example set: 🦆 String + WAH (touch-wah), 🎸 String + DRIVE (overdrive/fuzz), 🔥 String + TUBE (buizenversterker), 🔥 String + Tube, 🔁 Arp + String echo.
Editor: https://editor.musicbrain.nl
Sources & licences
AudioSynthKarplusStrongandAudioAmplifierfrom the Teensy Audio Library by Paul Stoffregen, PJRC (MIT licence). The browser version is a copy of that arithmetic under the same licence.- The MusicBrain wrapper is MIT licensed.
Versions
- 0.5.15: CV inputs for Pluck and Level.
- 0.5.13: first version, the first physical-modelling voice in the firmware.