# Blossa

> Reverb that blooms: it swells in behind notes, steps aside while you play, and can be gated shut for a hard stop.

- Engine id: `org.sournd.reverb.blossa`
- Category: Reverb
- Licence: paid: £2.99 an effect or £4.99 a synth, once (owned for good, with updates), or included in the Everything plan (£14.99 a month)
- Version: 1.0.0
- Latency: 0 samples
- Tail: 19 s
- Sidechain input: no
- Channels: mono or stereo
- Audio demo: https://sournd.com/static/preview/demos/blossa.mp3 (plucked chords, default settings)

## Parameters

The id is the C ABI parameter id and the JUCE parameter id (as a decimal string).

| Id | Key | Name | Min | Max | Default | Unit | Taper |
|---|---|---|---|---|---|---|---|
| 0 | `predelay_ms` | Pre-delay | 0 | 400 | 20 | ms | linear |
| 1 | `decay_s` | Decay | 0.2 | 12 | 3.5 | s | log |
| 2 | `damping_hz` | Damping | 1000 | 16000 | 5500 | Hz | log |
| 3 | `swell_ms` | Swell | 0 | 2000 | 300 | ms | linear |
| 4 | `duck` | Duck | 0 | 1 | 0.25 | - | linear |
| 5 | `gate` | Gate | 0 | 1 | 0 | - | linear |
| 6 | `threshold_db` | Gate threshold | -60 | 0 | -30 | dB | linear |
| 7 | `hold_ms` | Gate hold | 0 | 1000 | 180 | ms | linear |
| 8 | `release_ms` | Gate release | 5 | 1000 | 120 | ms | log |
| 9 | `width` | Width | 0 | 1 | 1 | - | linear |
| 10 | `mix` | Mix | 0 | 100 | 35 | % | linear |

## Use it in JUCE

CMake ([quick start](/docs/juce/index.md)):

```cmake
juce_add_module(path/to/sournd_engine)
target_include_directories(MyPlugin PRIVATE path/to/include)
target_link_libraries(MyPlugin PRIVATE sournd_engine path/to/libsournd_cabi.a)
```

C++:

```cpp
#include <sournd_engine/sournd_engine.h>

sournd::SourndEngine engine { "org.sournd.reverb.blossa" };
juce::AudioProcessorValueTreeState parameters { *this, nullptr, "Parameters",
    sournd::SourndEngineParameters::createLayout (engine) };
sournd::SourndEngineParameters bridge { engine, parameters };

// prepareToPlay
engine.prepare ({ sampleRate, (juce::uint32) maximumBlock, 2 });
bridge.prepare (sampleRate);
setLatencySamples ((int) engine.latency());

// processBlock
bridge.apply ((uint32_t) buffer.getNumSamples());
juce::dsp::AudioBlock<float> block { buffer };
engine.process (juce::dsp::ProcessContextReplacing<float> { block });

// get/setStateInformation: hold getCallbackLock() around saveState / loadState,
// so state work never overlaps processBlock (full example: /docs/juce/)
```

Plain C:

```c
sournd_engine *e = NULL;
if (sournd_engine_create("org.sournd.reverb.blossa", &e) == SOURND_OK) {
    sournd_engine_prepare(e, 48000.0, 512);
    sournd_engine_set_param(e, 0, 20); /* Pre-delay */
    sournd_engine_process(e, in, out, 2, frames);
    sournd_engine_destroy(e);
}
```

## How it is made

Original sOURnd design: fast and slow envelope followers drive a swell ratio on the reverb input and a ducking gain on the wet, a separate fast detector drives a hold/release gate, around a damped parallel comb bank with series all-pass diffusion per channel.

## Ask your AI

Paste this into your coding assistant:

```text
Add the sournd engine org.sournd.reverb.blossa to my JUCE plugin. Follow https://sournd.com/docs/juce/index.md
and the engine reference at https://sournd.com/engines/blossa/index.md. Expose every parameter through APVTS.
```