Hydra Midi

A utility script for using midi with https://hydra.ojack.xyz.

Usage

Start (and optionally show) midi and use midi inputs as parameters for hydra:

// You can either use `@latest` or load a specific version with, for example, `@0.4.3`.
await loadScript('https://cdn.jsdelivr.net/npm/hydra-midi@latest/dist/index.js')

// Use midi messages from all channels of all inputs.
await midi.start({ channel: '*', input: '*' })
// Show a small midi monitor (similar to hydra's `a.show()`).
midi.show()

// Use any note to control the red amount of hydra's `solid()` function.
solid(note('*'), 0, 1).out()

// Or, if you are using a midi controller and not a keyboard:
// Use a control change value to control the red amount.
// solid(cc(74), 0, 1).out()

Edit on hydra

CDN

All versions beginning from 0.4.0 can be loaded from npm:

https://cdn.jsdelivr.net/npm/hydra-midi@latest/dist/index.js

all previous versions are available directly from github:

https://cdn.jsdelivr.net/gh/arnoson/hydra-midi@0.3.1/dist/index.js

Examples

Use an envelope and scale it

await loadScript('https://cdn.jsdelivr.net/npm/hydra-midi@latest/dist/index.js')

// Use midi messages from all channels of all inputs.
await midi.start().show()

// Trigger an ADSR envelope each time the note C3 is played and scale
// the value to a range between 20 and 50.
osc(note('C3').adsr(300, 200, 1, 300).range(20, 50), 0, 0).out()

Edit on hydra

Use multiple midi controllers

await loadScript('https://cdn.jsdelivr.net/npm/hydra-midi@latest/dist/index.js')

await midi.start().show()

// Save input 0 (which in this is example could be a seaboard block) in a
// variable. As the seaboard is an MPE-keyboard it makes sense to listen to all
// channels by default.
seaboard = midi.input(0).channel('*')

// Save input 1 (for example a faderfox) in a variable. We don't specify the
// channel so it defaults to channel 0. To use another channel we have to select
// it explicitly in the `note()` or `cc()` functions.
faderfox = midi.input(1)

// Modulate the noise speed with the seaboard's CC74 values (of any channel).
noise(10, seaboard.cc(74))
  // Use any note on the seaboard to modulate the threshold.
  .thresh(seaboard.note('*').adsr().scale(0.6), 0.1)
  // Use the first 3 faders (which happen to be CC40–CC42 on channel 12) of the
  // faderfox to mix a color.
  .color(faderfox.cc(40, 12), faderfox.cc(41, 12), faderfox.cc(42, 12))
  .out()

Edit on hydra

Documentation

midi.start()

Start midi and optionally set default values. You have to call this function before using any midi functions. Note: It is important to wait the function, otherwise midi access isn't ready and you may not be able to target a specific midi input.

await midi.start({
  // Which input to use in `note()` and `cc()` by default.
  // Can be an input index, an input name or '*' to always listen to all inputs
  // by default.
  input: '*',

  // Which channel to use in `note()` and `cc()` by default.
  // Can be a channel index (0 -> midi channel 1, 1 -> midi channel 2, ...) or
  // '*' to always listen to all channels by default.
  channel: '*',

  // Default attack, decay, sustain and release values for the `adsr()` function
  // that can be chained to `note()`.
  adsr: [100, 100, 1, 100],
})

midi.show() / midi.hide()

Show / hide the midi monitor.

midi.input()

Use the specified input as default. (Doesn't change to global default input)

myKeyboard = midi.input(3)
// Listen to note 60 on the global default channel (defined in `midi.start()`)
//on input #3.
myKeyboard.note(60)

myController = midi.input(3).channel(15)
// Listen to CC74 on channel 15 on input #3.
myController.cc(74)

midi.channel()

Use the specified channel as default. (Doesn't change to global default channel)

ch16 = midi.channel(15)
// Listen to CC42 on midi channel 16 (-> channel index 15!).
ch16.cc(42)

note()

Listen to a note. Returns 1 if the notes is currently playing, 0 otherwise.

note(
  // Can be midi note number, a note name (like 'A3' or 'D#2') or '*' to listen
  // to any note.
  note,
  // A channel index between 0 and 15.
  channel?,
  // An input index or input name. (Show the midi monitor to see the indexes).
  input?
)

adsr()

Trigger an envelope each time a note is played. adsr()can only be used together with note.

// Attack, decay and release are specified in milliseconds, sustain is a factor
// between 0 and 1.
note('C3').adsr(attack, decay, sustain, release)

velocity()

Retrieves the latest velocity played for the note in a range from 0 to 1.

note('C3').velocity()

cc()

Listen to (normalized) CC values.

cc(
  // The CC index.
  index,
  // A channel index between 0 and 15.
  channel?,
  // An input index or input name. (Show the midi monitor to see the indexes).
  input?
)

.onNote()

You can define an event to trigger when a particular note is played on a specific input or channel:

myController = midi.input(3).channel(15)

myController.onNote('c1', () => osc().out())

Or listen to any note:

myController = midi.input(3).channel('*')

scene1 = () => solid(1, 0, 0).out()
scene2 = () => solid(0, 1, 0).out()

myController.onNote('*', ({ note, velocity, channel }) => {
  switch (note) {
    case 36: { scene1(); break; }
    case 37: { scene2(); break; }
  }
})

.onCC()

You can define an event to trigger when a particular CC is changing on a specific input or channel:

myController = midi.input(3).channel(15)

myController.onCC('1', () => osc().out())

Or listen to any CC:

myController = midi.input(3).channel('*')

myController.onCC("*", ({ index, value, channel }) => { 
  console.log("onCCevent")
  console.log(index) 
  console.log(value)
  console.log(channel)
});

### Transforms

Values from `note()`, `cc()` and `adsr()` can be transformed using the following functions:

#### scale()

Scale the value by a factor.

```js
note(60).adsr().scale(20)
cc(40).scale(3)

range()

Map the value to a different range.

cc(41).velocity().range(-0.5, 0.5)

value()

Apply custom transformations to a value.

note(60)
  .adsr()
  .value(v => Math.sin(v))

Accessing midi values directly

note() and cc() do not directly return the corresponding values. Instead they return a function. This is useful for usage as a parameter as the values are updated automatically:

// The color will get updated as soon as the value of CC40 changes.
solid(cc(40), 1, 1).out()

Together with the transforms this should be flexible enough. In same rare cases you might want to use the values directly. You can do so by prefixing the function with an underscore:

osc(() => _cc(40) * 2, 0, 0).out() // This could also be achieved with `scale()` or `value()`.

// This will only set the value when executing the script and won't update.
noteIsPlaying = _note(60)
solid(1, 0, 0).invert(noteIsPlaying).out()

Contribute

Contributions to the script and it's documentation are welcome :~) Please make sure you:

• use prettier to format your code (should happen automatically if you work on this project in VSCode)
• use conventional commits (these are used to automatically generate release messages, including credits for your contributions)

To test this script in development, run pnpm dev, which will

• compile (and watch) /src/index.ts
• start a local server in /dist
• tunnel it with untun
• open a new tab in your browser with an empty hydra sketch using your local development version of hydra-midi

If you have e.g. Firefox as your default browser but still want to open it in Chrome (needed for WebMidi) run pnpm dev:chrome.

Note: there is no automatic browser-reloading when your code has changed. Instead simply re-evaluate your sketch in hydra with Ctrl + Shift + Enter