jpcima / string-machine

Digital model of electronic string ensemble instrument

string-machine

This is a virtual-analog string ensemble synthesizer.

This implementation is based on a digital model designed by Peter Whiting. The improvement of the model adds various abilities, in particular a virtual-analog emulation of the bucket brigade delay circuit.

Contributors

Thanks to many persons who contribute to improve this project.

• S. M. "sm7x7" for providing presets
• Nicolas Faure "sub26nico", Erwan Lerale "r1" and Éric Forgeot "farvardin" for testing and feedback
• Olivier Humbert "trebmuh" for creating packages and redistributing

Download

Get from Open Build Service.

Change log

0.1.1 (dev)

This release breaks backwards compatibility.

• envelope generator fixed, rewritten as exponential AHDSR
• adjusted the value domain of controls to be more useful: detune, shape filters
• fixed computation errors regarding the filters
• implemented the bucket brigade delay
• provided two switchable chorus models, digital and BBD
• provided the Solina chorus as independent plugins, 1-in 2-out and 2-in 2-out
• supported dynamic changes of sample rate
• added support of MIDI controllers: volume, pan, expression

0.1.0

• initial release

Build instructions

1. Obtain prerequisites

Install needed packages:

• git
• build-essential
• pkg-config
• libx11-dev
• libgl-dev
• libcairo2-dev

2. Check out the repository and submodules

git clone https://github.com/jpcima/string-machine.git
cd string-machine
git submodule update --init

3. Compile

make

4. Install

To perform a system-wide installation:

sudo make install

Or, to install only for the current user:

make install-user

string-machine's Issues

Add pitch bend

Add pitch bend ability, on request of @sub26nico

Limit polyphony

I should introduce a polyphony limit such that CPU can be bounded, and prevent x-running on more limited hardware.

This should be allowed with a parameter in integer range.
[1-32] is reasonable.

Request - Presets

First : Thanks for this VST !

I see that there is a Preset section and some presets available in the source tree but I can't see them either in Carla or Ardour ?
Is there something I'm missing ?

Make the parameter changes smooth

Faust benchmark

Below are some measures of output throughput with faust bench.cpp. (GCC)

• fast-math is able to get a performance increase most of times
• vec is almost always a massive decrease

Edit: the data is a measure of throughput, which means higher = better.

Strange envelope behaviour

I'm not sure, whether this is intentional, but I'm experiencing strange behaviour of the ADSR envelope:

• The attack is still very slow at the lowest settings.
• If the sustain is 0 and decay > 0 and attack is 0, there is no sound, even when the decay is increased.
• Generally the envelope settings react in unexpected ways, which I haven't fully grasped yet.

Is this supposed to behave like a standard ADSR? I had a short look at the source code and AFAICS it doesn't mention any intended special behaviour.

Oscillator waveshaper aka "enhancer"

There exists an "enhance" setting which permits to set a bias prior to a clipping diode circuit.
It will allow to pass a part of the negative signal from the output of the "differentiated square" oscillator.

Zynthian: Push any key followed by the key one octave down, the second note doesn't play.

Observed on Zynthian.

1. I push C3 and don't release it -> I hear C3
2. I push any other key than C2. -> I hear the two notes
3. I release the second key -> I still hear C3
4. I push C2 -> I hear C3 only

Got the LV2 URI wrong

Following the compatibility break in the dev version, it needs to update plugin URI.
I want to append -mk2 as a prefix. (URL http://jpcima.sdf1.org/lv2/string-machine-mk2)

Problem: I thought to have done this in source, but mistook the variable, and instead I changed homepage.

Location of problem:

string-machine/plugins/string-machine/meta/DistrhoPluginInfo.h

Line 6 in 1240f54

#define DISTRHO_PLUGIN_HOMEPAGE "https://github.com/jpcima/string-machine-mk2"

The chorus creates gating effect

Using v0.1.0-125-g7050cb1

The chorus on the string seems to create a gating effect, or a clipping effect. The strings by themselves sound ok. If the string machine is fed into a separate chorus with a high enough dry level, it sounds a lot better.

Mac build universal binary

It needs i386 build for compatibility.

First MIDI note sticky in Zynthian MIDI player

Observed by two persons in Zynthian community:

Topic: https://discourse.zynthian.org/t/any-lv2-arp-solina-roland-rs-type-string-machines-solved/3627

The one strange new behavior I noted was that when running the Zynthian MIDI file player, the first note would stick as though no note off had been sent. When stuck notes were cleared with a Panic, all subsequent notes from the player seemed to hit their note-off events just fine. Stuck notes were not happening with the previous build.

Crash in Reaper on stopping and resuming midi track

@sub26nico:

jpcima, j'ai un bogue avec string-machine (VST) qui fait planter Reaper : si je charge string-machine dans une piste MIDI, quand je lance la lecture, ça fonctionne. Je stoppe puis relance la lecture et là, ça freeze l'IU de Reaper qui me dit 'Buffering' là où d'habitude il signale play ou record ou stop selon la situation
le terminal ne dit rien...
aucun souci dans Ardour avec le vst ou le lv2

Build failed (missing pugl)

tried running make and it failed

make -C dpf/dgl ../build/libdgl-cairo.a
make[1]: Entering directory '/home/reed/Desktop/string-machine/dpf/dgl'
Compiling src/ApplicationPrivateData.cpp
In file included from src/ApplicationPrivateData.cpp:20:
src/pugl.hpp:44:10: fatal error: pugl-upstream/include/pugl/pugl.h: No such file or directory
   44 | #include "pugl-upstream/include/pugl/pugl.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make[1]: *** [Makefile:180: ../build/dgl/ApplicationPrivateData.cpp.o] Error 1
make[1]: Leaving directory '/home/reed/Desktop/string-machine/dpf/dgl'
make: *** [Makefile:26: dgl] Error 2

I already have libpugl-dev installed. Using Ubuntu 22.04.

windows build instructions / cross-platform build using cmake?

I see that there is a windows build available. Is there information available on how that build was created? Maybe we can set up a cmake infrastructure to provide platform-independent builds.

String phaser

Since the string synthesizer is so commonly paired with the EHX small stone phaser, it will be interesting if this embeds its own analog phaser effect.
More so if the phaser is made compatible with stereo, to connect in series with the chorus.

This code implements a vintage phaser. Phase100.dsp.txt

Kiiski, R., Esqueda, F., & Välimäki, V. (2016).
Time-variant gray-box modeling of a phaser pedal.
In 19th International Conference on Digital Audio Effects (DAFx-16).

It's a 10-stage and quite different from the desired phaser; but the reference paper gives a method to extract modulation from any phaser.
It will serve if a volunteer owner of small stone or similar wants to contribute some measurements.

Completing the model

I've quickly checked the model against Solina schematics, identified major lacking elements.
(answering also @farvardin on completeness of implementation)

In the original, the 4' and 8' sections are known as violin and viola respectively.

1. missing: brass section (trumpet/horn)
   It's needed to identify what does the formant circuit folllowing the oscillator.
   It has a set of switches which seem to affect a characteristic of a filter.
   

2. missing: bass section
   It's cello and contrabass, and it has a more complex circuitry, of which I'm not fully sure how it fits in the model.
   It's made from various parts: low-tone selection, clipper, trigger suppression, bass sustain, and low-pass filter

Add scaling

Hi!

Thanks for the plugin!

I play with it on Linux connected to 4K monitor with 200% desktop environment scaling. The string-machine UI looks to tiny to deal with without magnifying glass (but sounding is appealing!). Please, add opportunity to scale UI up.

Pwm oscillator

It's available in pwm branch.

demo: pwm.flac.gz
PWM off vs PWM 100% 0.6Hz

cc @farvardin if you are interested to review the feature

No install target

Please see how the Arch Linux installs it manually: https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=string-machine-git

Infinite loop?

https://github.com/jpcima/string-machine/blob/master/tests/string-osc/sources/string-machine

Carla does not update knobs on program change

from #lad IRC: if I choose the presets in carla they also do not update the graphical knobs

Implement Hold pedal

as the title says

Raspberry pi build fail

cannot compile due to compile options -msse -msse2

root@zynthian:/media/usb/Develop/string-machine# make
make -C dpf/dgl ../build/libdgl-cairo.a
make[1]: Entering directory '/media/usb0/Develop/string-machine/dpf/dgl'
Compiling src/Application.cpp
g++: error: unrecognized command line option ‘-msse’; did you mean ‘-fdse’?
g++: error: unrecognized command line option ‘-msse2’

Include version number in source code

Hi there, thanks for this awesome plugin. I had been hoping for a release of a good Open Source string machine plugin for a long time.

I'm in the process of packaging the plugin for the Arch User Repository. I'll do a package for the release version (0.1.0) and a VCS package, which always compiles the latest state of the Git repo. For the latter it would be helpful, if the version number of the software was included somewhere in the sources. so my PKGBUILD can extract it.

The obvious place would be the #define on line 8 of plugins/string-machine/DistrhoPluginInfo.h, e.g.:

#define DISTRHO_PLUGIN_VERSION         0,1,0

Also, an "install" target in the Makefile would be nice, but I guess that should be raised as an issue with DPF.

"Canvas does not allow drawing" error on Windows

When I open string machine's GUI (VST2) on hosts like REAPER and MidiPlayer6, the GUI will crash occasionally. At this time, the host UI may crash altogether.

On MidiPlayer6, it gives me those errors:

(Notice the font in the third image, which only appears on critical UI rendering issues.)

PWM oscillator should be a square at zero position

Default oscillator setting is a pulse of 0.1% duty.
Needs to review the control model of PWM oscillator.

Analog delay compander

Huovilainen, Antti. "Enhanced digital models for analog modulation effects." Proc. Int. Conf. Digital Audio Effects (DAFx-05), Madrid, Spain. 2005.

See 5.2