# Piano keyboard

> A clickable piano keyboard for Python synthesizers — glissando, velocity, lit notes from MIDI or a sequencer, and computer-keyboard playing.

Source: https://albakore.github.io/pyzed/audio/components/piano/

(Image: A four-octave keyboard lighting up a chord progression and an arpeggio)

**In plain words:**

A keyboard you can play with the mouse: click a key to play a note, drag across the keys to
slide from one to the next. Notes played from elsewhere (a MIDI keyboard, a sequencer) light up.

```python
from pyzed import audio, ui

engine = audio.Engine()
synth = engine.add("midi_in")  # notes from note_on/note_off reach the midi_in modules
...

ui.audio.Piano(start=48, octaves=3, pressed=sorted(self.held),
               on_note_on=lambda e: engine.note_on(e.value.note, e.value.velocity),
               on_note_off=lambda e: engine.note_off(e.value))
```

## Notes and velocity

Notes are MIDI numbers: 60 is middle C (C4), 69 is the A at 440 Hz. `note_on` gives a
`Note(note, velocity)`; the lower on a key you click, the louder (velocity 30 to 127).
`note_off` gives the note number. Dragging across keys releases one and presses the next.

`ui.audio.note_name(61)` gives `"C#4"`, handy for labels.

## Playing from the computer keyboard

`ui.audio.KEYBOARD` maps keys to semitones like most music apps: the row `a s d f g h j k`
is the white keys and `w e t y u o p` the black ones.

```python
def on_key(self, combo):
    if combo in ui.audio.KEYBOARD and combo not in self.keys:
        self.keys.add(combo)
        note = self.octave * 12 + ui.audio.KEYBOARD[combo]
        engine.note_on(note)

def on_key_up(self, key):
    if key in self.keys:
        self.keys.discard(key)
        engine.note_off(self.octave * 12 + ui.audio.KEYBOARD[key])
```

| Property | Default | What it does |
| --- | --- | --- |
| `start` | `48` | The first note (rounded down to a C). |
| `octaves` | `2` | How many octaves (plus the last C). |
| `pressed` | `()` | Notes to light, played from elsewhere. |
| `color` | `"accent"` | Color of pressed keys. |
| `key_width`, `height` | `24`, `110` | Size of a white key. |
| `labels` | `True` | Writes the name of every C. |

Events: `on_note_on` (`Note(note, velocity)`), `on_note_off` (the note number).