Octavian

Octavian is a little utility library for working with musical notes and their frequencies. Super cool, right?

Installation

First things, first: how do I install this thing?

npm install octavian

Maybe you even throw a --save in there if you feel like keeping it around.

Usage

So, we've got Octavian installed, how do we use it?

var Octavian = require('octavian');

var note = new Octavian.Note('A4');

Or, if you're some kind of hipster…

var Note = require('octavian').Note;

var note = new Note('A4');

The Basics

A Note has a few properties that we can play around with.

var note = new Note('A#4');

note.letter; // 'A'
note.modifier; // '#'
note.octave; // 4
note.signature; // 'A#4'
note.pianoKey; // 50
note.frequency; // 466.164

Normalization

But, what if we toss in some bogus note? Something like E#, maybe? There is no E#, right?

var note = new Note('E#5');

note.signature; // 'F5'

Intervals

Music is all about intervals. We can move up by a semitone or some other interval.

var note = new Note('C3');

note.majorThird(); // returns a new Note('E3');
note.perfectFifth(); // returns a new Note('G3');
note.perfectOctave(); // returns a new Note('C4');

You can do any of the following:

downOctave()
minorSecond()
majorSecond()
minorThird()
majorThird()
perfectFourth()
diminishedFifth()
perfectFifth()
minorSixth()
majorSixth()
minorSeventh()
majorSeventh()
perfectOctave()

There are also some extra methods that are aliased, if you'd prefer:

augmentedFourth()
third()
fifth()

Chords

You can create chords with Octavian.

const cMajorChord = new Octavian.Chord('C4', 'major');

cMajorChord.notes; // returns [ { letter: 'C', modifier: null, octave: 4 },
                   //           { letter: 'E', modifier: null, octave: 4 },
                   //           { letter: 'G', modifier: null, octave: 4 } ]

cMajorChord.signatures;  // returns [ 'C4', 'E4', 'G4' ]
cMajorChord.frequencies; // returns [ 261.626, 329.628, 391.995 ]
cMajorChord.pianoKeys;   // returns [ 40, 44, 47 ]

You can create the following chords:

major
majorSixth
majorSeventh
majorSeventhFlatFive
majorSeventhSharpFive
minor
minorSixth
minorSeventh
minorMajor
dominantSeventh
diminished
diminishedSeventh
halfDimished

You're also more than welcome to use the following aliases for any of the above:

maj is an alias for major
6 is an alias for majorSixth
maj6 is an alias for majorSixth
7 is an alias for majorSeventh
maj7 is an alias for majorSeventh
maj7b5 is an alias for majorSeventhFlatFive
maj7#5 is an alias for majorSeventhSharpFive
min is an alias for minor
m is an alias for minor
min6 is an alias for minorSixth
m6 is an alias for minorSixth
min7 is an alias for minorSeventh
m7 is an alias for minorSeventh
m#7 is an alias for minorMajor
min#7 is an alias for minorMajor
m(maj7) is an alias for minorMajor
dom7 is an alias for dominantSeventh
dim is an alias for diminished
dim7 is an alias for diminishedSeventh
m7b5 is an alias for halfDiminshed

Adding Notes to a Chord

You can add notes to a chord manually, if that suits you:

const chord = new Octavian.Chord('C4');

chord.signatures; // returns ['C4']

chord.addInterval('majorThird');
chord.signatures; // returns ['C4', 'E4']

chord.addInterval(7);
chord.signatures; // returns ['C4', 'E4', 'G4']

Turning a Note into a Chord

You can turn any note into the basis for a chord:

const note = new Octavian.Note('C4');
note.toChord(); // returns a new chord with only C4 in it.
note.toChord('major'); // returns a new chord with C4, E4, and G4 in it

dgrmunch/octavian