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Bifurcator documentation

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doc/4-instrument/bifurcator.md Normal file
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# Bifurcator instrument editor
Bifurcator instrument editor consists of these macros:
- **Volume**: volume sequence.
- **Arpeggio**: pitch sequence.
- **Parametet**: set parameter of logistic map function.
- **Panning (left)**: output level for left channel.
- **Panning (right)**: output level for right channel.
- **Pitch**: fine pitch.
- **Load Value**: changes the current output value.
## audio generation description
Bifurcator uses logistic map iterations for sound generation.
basically it runs the following function over and over:
```
r = (1 + (p / 65536)) * 2
x = (r * x) * (1 - x)
```
where `x` is the current output value and `p` is the "parameter".
by varying the parameter, the value of x may change drastically, producing a variety of sounds.
the higher the parameter, the more "chaos" is present, effectively yielding noise.
the default parameter is `47360`, which results in a square wave.
if the parameter is set to 0, there's no sound at all.
as the parameter approaches 32768, a decaying square wave is produced.
the square wave stops decaying past 32768 and becomes louder until the parameter hits ~47496 (`r = 1 + sqrt(6)`).
a second square wave one octave lower then starts appearing, until the parameter reaches ~51443 (`r ≈ 3.56995`). this is where chaos begins.
anything higher results in a total mess.
## the importance of loading the value
you must load a value that isn't 0 in order to get sound. otherwise the function will always output 0.

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doc/7-systems/bifurcator.md
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# Bifurcator
this is a fantasy sound chip which uses a unique sound generation method: logistic map iterations.
## effects
- `10xx`: **set low byte of channel sample state.**
- `11xx`: **set high byte of channel sample state.**
- `12xx`: **set parameter low byte.**
- `13xx`: **set parameter high byte.**
## info
this chip uses the [Bifurcator](../4-instrument/bifurcator.md) instrument editor.