# Synthesizer

> A playable synthesizer with effects in Python — two oscillators, a resonant filter, an envelope, distortion, chorus, delay and reverb, with FL Studio-style knobs and a piano.

Source: https://albakore.github.io/pyzed/audio/demos/synth/

(Image: A synthesizer panel: knobs in four sections, an oscilloscope, a spectrum, a volume fader and a piano being played)

A complete synthesizer in about 200 lines: [`examples/audio/synth.py`](https://github.com/albakore/pyzed/blob/main/examples/audio/synth.py).

```bash
python examples/audio/synth.py
```

Play it with the mouse on the piano or with the computer keys: <kbd>A</kbd> <kbd>W</kbd>
<kbd>S</kbd> <kbd>E</kbd> <kbd>D</kbd>… are the white and black keys of one octave, and <kbd>Z</kbd>
and <kbd>X</kbd> move the octave down and up. The three buttons at the top load presets
(Bass, Lead, Pad).

**In plain words:**

The sound is made by the engine; this file is only the panel. Every knob sets one value of a
module, and the displays read what comes out.

## How it is built

The patch is a chain of engine modules:

```
MIDI in → 2 oscillators → mixer → filter → amplifier → distortion → chorus → delay → reverb → speakers
                                   ↑            ↑
                                   └── envelope ┘
```

`midi_in` turns `engine.note_on()` into a pitch and a gate; the envelope opens the filter and
the amplifier on every note. The panel keeps a dictionary of values and one function, `put`,
sends each one to the module it controls:

```python
def put(self, key, value):
    self.values[key] = value
    if key in ("cutoff", "resonance"):
        self.engine.set(self.vcf, key, value)
    elif key in ("attack", "decay", "sustain", "release"):
        self.engine.set(self.env, key, value)
    ...
```

The view is made of [knobs](https://albakore.github.io/pyzed/audio/components/knob/) grouped in sections, a
[scope](https://albakore.github.io/pyzed/audio/components/scope/) and a [spectrum](https://albakore.github.io/pyzed/audio/components/spectrum/) reading
`engine.scope()` and `engine.spectrum()`, a [VU meter](https://albakore.github.io/pyzed/audio/components/vu-meter/), a
[fader](https://albakore.github.io/pyzed/audio/components/fader/) for the volume and a [piano](https://albakore.github.io/pyzed/audio/components/piano/)
whose `note_on`/`note_off` events go to the engine. `pz.frames()` redraws the window every
frame so the displays move.