A Note is the most abstract representation of pitch, in that it's simply an unparsed bit of text representing that pitch. Given a Scale, it's expected to name a val call exported by that scale.

A Pitch is a parsed Note. Functions that want to manipulate notes in a scale-independent way can ask the scale to convert to and from a Note. Not all scales use all the fields.

A scale degree, without reference to an octave.

Just a way to label an octave, either relative or absolute.

A PitchClass maps directly to a scale degree, which is a letter in traditional Western notation, though this PitchClass may have fewer or greater than 7 notes. The PitchClass is absolute in that it doesn't depend on the tonic of a key.

These numbers are expected to wrap around at the octave, so they usually use modular arithmetic, but if an octave is not handy (i.e. they're not in a Pitch), then steps exceeding an octave will be wrapped into an octave when one is available.

Positive for sharps, negative for flats.

Number of semitones. This is an absolute measure from octave 0, regardless of whether the scale has notes at octave 0. This is so you can convert between Semis and the similarly absolute Pitch in the same way for all scales.

This is like Semi, but floating point.

This is a relative amount of transposition. It could be either chromatic or diatonic.

Add diatonic steps. This doesn't deal with key signatures or non-diatonic scales.

The middle octave. The "center" of a scale should be oriented around this.

A physically played note on some input device. This hasn't been mapped to a scale yet, so the Pitch is in the context of the device's layout.

I have 3 kinds of kbds:

ASCII has 10 white keys, and black keys between each one. It should be relative, so that C or sa is always on Q and Z, and if the octave is <10 then it will wrap on the same row.

MIDI has the usual piano layout. It's absolute, so that a relative scale can start at keys other than C, if that would be convenient for the layout. The octave is rounded up to the nearest multiple of 7, and the extra keys are unused, so the octave always starts at C.

Continuum has no keys, just NNs. So it gets the scale degree that's closest to the given NN. That's different from the MIDI kbd because the MIDI kbd never wants a key to emit something between notes. TODO not supported yet

A number between -1 and 1 exclusive, representing the portion of the way between two scale degrees. I could have used "Cents" for this, but that implies equal temperedness.

This is equal tempered scale notes with the same definition as MIDI, so MIDI note 0 is NoteNumber 0, at 8.176 Hz, and is -1c. Middle C (4c) is NoteNumber 60.

PSignals are converted into this before performance since performance doesn't understand scales.

True if the NoteNumbers are close enough that they sound the same.

This is absolute non-logarithmic frequency.

Negative hz will result in NaN. TODO take an abs or throw an error, or let the NaN propagate?

Usually this means to use the scale currently in scope.

A generic transposition, for operations that can transpose diatonically, chromatically, or by absolute NoteNumber.

Diatonic transposition often requires a Key for context.

This is not very strongly typed, because it's intended to be scale independent, and not every scale will have the same values for key and mode.