spec: basic sketch of the specification

README.md

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+# sunny
+
+A control voltage and gate processor for Eurorack and other 1V/Oct systems.
+
+## Language
+
+The `sunny` control language is based on the concept of channels.
+Each channel consists of one CV (analog) output and
+one gate (digital) output.
+
+Each track has an associated octave value, by default 4, in which it will
+play note values.
+
+### Values
+
+- Note values, either **simple** like `C`, `A#`, and `Db`,
+**relative** like `C=` (C in this octave), `D+` (D in the next octave),
+or `A-` (A one octave down),
+or **absolute** like like `C2`, `Ab4`, or `F#0`.
+Where a note value is needed, a voltage value (as below) can be substituted, prefixed with a `v`, like `v12c`.
+
+- Voltage values, which can be expressed in volts (like `2v`), millivolts
+(like `2330mv`), cents (like `220c`), semitones (like `4c`), or octaves (like `1o`), and which can be **absolute** or **relative** (like `+2c`).
+Where a voltage value is needed, a note value (as above) can be substituted, prefixed with an `n`, like `n2C#`.
+
+- Conf(iguration) values, which are used to set up channel parameters,
+are either integers or real numbers (as context dictates) which can be
+**absolute** or **relative**, and are sometimes **optional**, allowing the values "off" and "none".
+
+- Boolean values, which can be `true` (or `on`) or `false` (or `off`).
+
+- Time values, which are either `s`econds or `u` (milliseconds), or the special value `beat` which refers to one beat based on the BPM of the channel.
+
+### Building Blocks
+
+- `set <volts>` (abbr. `s`) sets the CV value of the channel to a given value.
+This value can be given in `c`ents, `s`emitones (which is the default),
+`o`ctaves, or 
+
+- `play <note>` (abbr. `n`) sets the CV value to a given value and turns on and off the digital output for one beat minus the trigger amount (or simply leaves it on if legato is configured).
+
+- `wait <time>` (abbr. `w`) makes the program wait until the next value.
+Without the use of wait, all changes are executed simultaneously and
+the output will simply be the last values set on the channel.
+
+- `off` (abbr. `o`) turns off the digital channel.
+
+- `trigger` (abbr. `t`, `trg`, `trig`) turns on the digital channel for a
+very short time, then turns it off.
+
+- `gate` (abbr. `g`, `gte`) turns on the digital channel until it is turned off again.
+
+### Channel Control
+
+- `octave <int>` sets the octave, between 0 and 8, to which simple and relative note values will be played.
+
+- `bpm <natural>` sets the tempo of the channel. This is the time used by the time value `beat` and by the `play` instruction.
+
+- `portamento <optional natural>` turns on or off portamento (a slide between CV values) and sets its slope.
+
+- `legato <boolean>` turns on or off legato. When legato is on, the `play` instruction will not set the gate output to zero at the end of the note.