geikha / hydra-midi

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

Hydra Midi

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

Important

Showing the GUI (midi.show()) is only working when you re-run the script, should be fixed soon.

Usage

Visit https://hydra.ojack.xyz. The Hydra Midi Extension will get activated automatically.

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

await loadScript('https://cdn.jsdelivr.net/gh/arnoson/hydra-midi/dist/index.js')

// Use midi messages from all channels of all inputs.
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

Examples

Use an envelope and scale it

await loadScript('https://cdn.jsdelivr.net/gh/arnoson/hydra-midi/dist/index.js')

// Use midi messages from all channels of all inputs.
midi.start({ input: '*', channel: '*' })
midi.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/gh/arnoson/hydra-midi/dist/index.js')

midi.start()
midi.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.

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: 0,

  // 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: 0,

  // 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)

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?
)

Transforms

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

scale()

Scale the value by a factor.

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

range()

Map the value to a different range.

cc(41).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 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()