Tonal

• PDegree: Map scale index degree to MIDI notes in scale.
• PFilterByKey: Filter notes based on their presence in key.
• PNearestNoteInKey: Return the nearest note in key.
• PMidiNoteToFrequency: Map MIDI note to frequency value.
• PMidiSemitonesToFrequencyRatio: Map a MIDI offet in semitones to a frequency ratio.
• PKeyTonic: Given a Key as an input, returns the tonic of that key.
• PKeyScale: Given a Key as an input, returns the scale corresponding to the key.