chord_transposer

Description:

chord transposer

A Dart package for transposing chords into any given key.
Features #

Transpose chords from one key to another
Transpose chords up or down semitones
Find chords in lyrics and transpose them into another key
Find chords in lyrics and transpose up or down semitones

Usage #
First initialize the ChordTransposer:
final transposer = ChordTransposer();
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Transpose chords #
Transpose a single chord from one key to another:
transposer.chordToKey(chord: 'D/F#', fromKey: 'A', toKey: 'G'); // => C/E
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Transpose multiple chords from one key to another. If fromKey is not given, it will use the first chord in the list:
transposer.chordsToKey(chords: ['C', 'F', 'Am', 'G7', 'Bdim'], toKey: 'E'); // => [E, A, C#m, B7, D#dim]
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Transpose a single chord up or down semitones:
transposer.chordUp(chord: 'D', semitones: 5); // => G
transposer.chordDown(chord: 'Bb', semitones: 2); // => Ab
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Transpose multiple chords up or down semitones:
transposer.chordsUp(chords: ['D','Aadd9'], semitones: 4); // => [Gb, Dbadd9]
transposer.chordsDown(chords: ['Bb7/D', 'Eb'], semitones: 6); // => [E7/G#, A]
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Transpose lyrics #
final lyrics = '''
[C]Twinkle, twinkle [F]little [C]star.
[F]How I [C]wonder [G7]what you [C]are.
''';
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Tranpose lyrics from one key to another. If fromKey is not given, it will use the first chord in the lyrics. When ignoreInvalids is set to true (default), it will ignore all invalid chords. When it is set to false, it will throw an error if there is an invalid chord:
transposer.lyricsToKey(lyrics: lyrics, fromKey: 'C', toKey: 'G'); // =>
// [G]Twinkle, twinkle [C]little [G]star.
// [C]How I [G]wonder [D7]what you [G]are.
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Transpose lyrics up or down semitones:
transposer.lyricsUp(lyrics: lyrics, semitones: 5); // =>
// [F]Twinkle, twinkle [A]little [F]star.
// [Bb]How I [F]wonder [C7]what you [F]are.

transposer.lyricsDown(lyrics: lyrics, semitones: 3); // =>
// [A]Twinkle, twinkle [D]little [A]star.
// [D]How I [A]wonder [E7]what you [A]are.
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Additional information #
This package built to work with paurakhsharma's flutter_chord package and was inpsired by ddycai's chord-transposer npm package.