Koto - Music performing filesystem

Koto is a music performing filesystem, or a filesystem (sound) synthesizer. Koto allows to perform sound and music by interaction with mounted FUSE filesystem. If you don't make sense with it, check this demo movies below.

• filesystem performance
• filesystem performance 2
• simple performance (without filesystem feature)

Koto uses and depends on Tapirus sound synthesizer modules.

Dedicated with you.

Requirements

GNU/Linux

• libasound (ALSA)
• libfuse (>= 2.6.0)

macOS

• osxfuse

Installation

Pre-built binaries are available from here.

If you want to build, clone and type cargo build.

Usage

Command line usage

Koto uses FUSE filesystem as user interface, so, we should create mountpoint and mount it at first. To start and stop Koto simply, type like this:

# start koto
$ /path/to/koto /path/to/mountpoint

# stop koto
$ fusermount -u /path/to/mountpoint

Koto takes one positional arg MOUNTPOINT and some options. Important option in those is -c (--config). This specified initial configuration of synthesizer modules. Because of this Koto can start music by specified configuration. If you try it, type like this:

$ cd /path/to/koto
$ ./koto /path/to/mountpoint -c ./configure.lisp

When you think about to stop performace with Koto, you might want to save current configuration, to resume performance after like drinking a cup of tea. It's times like these, you can save entire synthesizer configuration (includeing sequencer pattern and wavetable values). To save the configuration, send a SIGUSR1 signal to the running Koto process, so a file koto.yyyymmddThhmmss.lisp is created in the directory placed Koto binary.

Basic concepts of Koto

Koto is a real-time sound processing system and we can interact via user interface. The UI is a filesystem. Koto has sound processing modules in it, these construct a graph that has a root as speaker output. Each sound processing modules, are like oscillators, effects or sequencers, have some parameters (e.g. delay time, etc.).

In Koto, one sound module are mapped as a directory. And, one parameter of sound module are mapped as a file or a diretory in the sound module directory.

Interact with Koto

Let's see some examples.

If you launch Koto with no configuration file, Koto mount specified directory, then start sound processing with no sound.

$ koto ./mountpoint
$ ls ./mountpoint
src0.val  vol.val
$ cat ./mountpoint/src0.val ; echo
0
$ cat ./mountpoint/vol.val ; echo
0

This is initial configuration. In this case, the root module has two parameters: src0 and vol. File extension .val tells to Koto that "it's a static value." In Koto, filename is important thing to know what kind of sound module the file/directory is. vol.val is zero, so we should change this value. To change value, simply write, like this:

$ cat ./mountpoint/vol.val ; echo
0
$ echo 0.3 > ./mountpoint/vol.val
$ cat ./mountpoint/vol.val ; echo
0.3

vol.val is changed but still no sound. So let's play sine wave. Because this filesystem is a user interface, we can add sine wave with manipulating filesystem. So we will delete src0.val, create a directory named src0.sine, set frequency as a file and request updation to Koto. Like this:

$ cd ./mountpoint
# delete value module
$ rm src0.val
# create sine module (but not connected)
$ mkdir src0.sine
# set frequency of sine module
$ echo 440 > src0.sine/freq.val
# tell koto a request to connect sine module
$ touch src0.sine/

Now we have 440 Hz sine wave.

Sound modules

Koto has some sound modules. Here is a list of modules and its parameters.

Oscillators

• rand: noise generator
  • freq: a sample time to renew output value.
• sine: sine wave generator
  • init_ph: initial phase of oscillator. for phase distortion synthesis.
  • freq: a frequency of this oscillator
• tri: triangle wave generator
  • init_ph: initial phase of oscillator. for phase distortion synthesis.
  • freq: a frequency of this oscillator
• saw: saw wave generator
  • init_ph: initial phase of oscillator. for phase distortion synthesis.
  • freq: a frequency of this oscillator
• pulse: pulse (square) wave generator
  • init_ph: initial phase of oscillator. for phase distortion synthesis.
  • freq: a frequency of this oscillator.
  • duty: duty ratio.
• phase: phase ocsillator utility for wavetable
  • it restrict input in range of [0.0, 1.0]
  • osc: phase source.
• wavetable: wave table oscillator
  • NOTE: now this module interporate linear between table samples.
  • table: wave table.
  • ph: phase source.

Sequencers

• trig: envelope trigger
  • eg: main envelove generator. trig returns this module's value.
  • srcN: other envelove generators triggered by trig. output is discarded. rest parameter.
• adsr: ADSR envelop generator
  • a: attack value in sec.
  • d: decay value in sec.
  • s: sustin value in range of [0.0, 1.0].
  • r: release value in sec.
• seq: Sequencer
  • pattern: sequencer pattern.
  • osc: oscillator.
  • osc_mod: frequency modulator for the osc.
  • eg: envelope generator. it's triggered by seq.

Effects

• lpf: simple low-pass filter
  • freq: cutoff frequency.
  • q: filter resonance.
  • src: filter source.
• delay: mono delay
  • time: delay time in sec.
  • feedback: feedback volume in percent.
  • mix: mix in percent.
  • src: delay source.

Utilities

• pan: panning utility
  • pan: pan value. left is -1.0, right is 1.0.
  • src: source.
• clip: clipping utility
  • min: min value.
  • max: max value.
  • src: source.
• offset: offset utility
  • val: base value
  • src: source.
• gain: gain utility
  • gain: gain multiplyer
  • src: source.
• +: signal addition utility
  • srcN: signal sources. rest parameter.
• *: signal multiplying utility
  • srcN: signal sources. rest parameter.
• out: mixing utility with volume
  • vol: volume
  • srcN: signal sources. rest parameter.

Author

• TANAKA Shinichi (shinichi.tanaka45@gmail.com)

License

This program koto is licensed under the GNU General Public License Version 3. See LICENSE for details.