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Chord API Reference

Complete API documentation for the Chord class.

Class Definition

namespace MusicTheory; public sealed class Chord : IEquatable<Chord> { public Note Root { get; } public ChordType Type { get; } public ChordQuality Quality { get; } }

Constructors

Chord(Note, ChordType)

Creates a new chord with the specified root note and chord type.

public Chord(Note root, ChordType type)

Parameters:

  • root: The root note of the chord

  • type: The chord type (Major, Minor7, Dominant13, etc.)

Example:

var cMajor = new Chord(new Note(NoteName.C, 4), ChordType.Major); var dm7 = new Chord(new Note(NoteName.D, 4), ChordType.Minor7); var g13 = new Chord(new Note(NoteName.G, 4), ChordType.Dominant13);

Chord(Note, ChordQuality) [Legacy]

Creates a new chord with basic quality (for backward compatibility).

public Chord(Note root, ChordQuality quality)

Parameters:

  • root: The root note of the chord

  • quality: The basic chord quality (Major, Minor, Diminished, Augmented)

Note: This constructor maps to basic triad types. Use the ChordType constructor for extended chords.

Example:

var cMajor = new Chord(new Note(NoteName.C, 4), ChordQuality.Major);

Properties

Root

public Note Root { get; }

Gets the root note of the chord.

Type

public ChordType Type { get; }

Gets the chord type (40+ types available).

Quality

public ChordQuality Quality { get; }

Gets the basic quality (Major, Minor, Diminished, Augmented). Derived from Type.

Instance Methods

GetNotes()

Gets all notes in the chord.

public IEnumerable<Note> GetNotes()

Returns: The chord tones in ascending order

Example:

var cMaj7 = new Chord(new Note(NoteName.C, 4), ChordType.Major7); var notes = cMaj7.GetNotes().ToList(); // [C4, E4, G4, B4]

GetSymbol()

Gets the chord symbol notation.

public string GetSymbol()

Returns: Standard chord symbol (e.g., "C", "Dm7", "G13", "F#maj7")

Examples:

  • Major → "C"

  • Minor → "Cm"

  • Major7 → "Cmaj7"

  • Dominant7 → "C7"

  • Minor7Flat5 → "Cm7b5"

  • Diminished7 → "C°7"

Transpose(Interval, Direction?)

Transposes the chord by the specified interval.

public Chord Transpose(Interval interval, Direction direction = Direction.Up)

Parameters:

  • interval: The interval to transpose by

  • direction: The direction (Up or Down), default is Up

Returns: A new Chord instance with transposed root

Example:

var c7 = new Chord(new Note(NoteName.C, 4), ChordType.Dominant7); var f7 = c7.Transpose(new Interval(IntervalQuality.Perfect, 4));

TransposeBySemitones(int)

Transposes the chord by a number of semitones.

public Chord TransposeBySemitones(int semitones)

Parameters:

  • semitones: Number of semitones (positive = up, negative = down)

Returns: A new Chord instance

GetEnharmonicEquivalent()

Gets the enharmonic equivalent of this chord.

public Chord? GetEnharmonicEquivalent()

Returns: The enharmonic equivalent, or null if root has no enharmonic

Example:

var cSharpMajor = new Chord(new Note(NoteName.C, Alteration.Sharp, 4), ChordType.Major); var dFlatMajor = cSharpMajor.GetEnharmonicEquivalent(); // Db major

AddExtension(int, IntervalQuality) [Legacy]

Adds an extension to the chord (for backward compatibility).

public Chord AddExtension(int degree, IntervalQuality quality)

Note: This method is maintained for backward compatibility. Prefer using specific ChordType values.

ToString()

Returns a string representation of the chord.

public override string ToString()

Format: Same as GetSymbol()

Equals(Chord?)

Determines if this chord equals another chord.

public bool Equals(Chord? other)

Note: Compares root note and chord type.

GetHashCode()

Returns the hash code for the chord.

public override int GetHashCode()

Static Methods

GetIntervalsForChordType(ChordType)

Gets the intervals that define a chord type.

public static List<Interval> GetIntervalsForChordType(ChordType type)

Parameters:

  • type: The chord type

Returns: List of intervals from the root

Example:

var major7Intervals = Chord.GetIntervalsForChordType(ChordType.Major7); // [Unison, Major 3rd, Perfect 5th, Major 7th]

Operators

Equality Operators

public static bool operator ==(Chord? left, Chord? right) public static bool operator !=(Chord? left, Chord? right)

Compare chords by root and type.

ChordType Enumeration

The library supports 40+ chord types:

Triads

  • Major

  • Minor

  • Diminished

  • Augmented

Seventh Chords

  • Major7

  • Minor7

  • Dominant7

  • MinorMajor7

  • HalfDiminished7 (Minor7Flat5)

  • Diminished7

  • Augmented7

  • AugmentedMajor7

Extended Chords

  • Major9, Minor9, Dominant9

  • Major11, Minor11, Dominant11

  • Major13, Minor13, Dominant13

Altered Chords

  • Dominant7Flat5

  • Dominant7Sharp5

  • Dominant7Flat9

  • Dominant7Sharp9

  • Dominant7Sharp11

  • Dominant7Flat13

Suspended Chords

  • Sus2

  • Sus4

  • Dominant7Sus2

  • Dominant7Sus4

Add Chords

  • Add9, MinorAdd9

  • Add11, MinorAdd11

  • Add13, MinorAdd13

Other Types

  • Power (root + fifth)

  • Major6, Minor6

  • Dominant6

  • MinorMajor9

Common Patterns

Creating Common Chords

// Basic triads var c = new Chord(new Note(NoteName.C, 4), ChordType.Major); var dm = new Chord(new Note(NoteName.D, 4), ChordType.Minor); var bdim = new Chord(new Note(NoteName.B, 4), ChordType.Diminished); // Seventh chords var cmaj7 = new Chord(new Note(NoteName.C, 4), ChordType.Major7); var dm7 = new Chord(new Note(NoteName.D, 4), ChordType.Minor7); var g7 = new Chord(new Note(NoteName.G, 4), ChordType.Dominant7); // Extended chords var cmaj9 = new Chord(new Note(NoteName.C, 4), ChordType.Major9); var dm11 = new Chord(new Note(NoteName.D, 4), ChordType.Minor11); var g13 = new Chord(new Note(NoteName.G, 4), ChordType.Dominant13);

Working with Progressions

// ii-V-I progression var progression = new[] { new Chord(new Note(NoteName.D, 4), ChordType.Minor7), new Chord(new Note(NoteName.G, 4), ChordType.Dominant7), new Chord(new Note(NoteName.C, 4), ChordType.Major7) }; // Transpose to different keys var interval = new Interval(IntervalQuality.Perfect, 4); // Up a 4th var transposed = progression .Select(chord => chord.Transpose(interval)) .ToArray(); // Gm7 - C7 - Fmaj7

Chord Analysis

public class ChordAnalyzer { public static string AnalyzeChord(Chord chord) { var notes = chord.GetNotes().ToList(); var intervals = notes.Skip(1) .Select(note => Interval.Between(chord.Root, note)) .ToList(); var analysis = new StringBuilder(); analysis.AppendLine($"Chord: {chord.GetSymbol()}"); analysis.AppendLine($"Root: {chord.Root}"); analysis.AppendLine($"Notes: {string.Join(", ", notes)}"); analysis.AppendLine($"Intervals: {string.Join(", ", intervals)}"); return analysis.ToString(); } }

Building Custom Chord Collections

// All diatonic seventh chords in C major var cMajorSevenths = new[] { new Chord(new Note(NoteName.C, 4), ChordType.Major7), // Imaj7 new Chord(new Note(NoteName.D, 4), ChordType.Minor7), // ii7 new Chord(new Note(NoteName.E, 4), ChordType.Minor7), // iii7 new Chord(new Note(NoteName.F, 4), ChordType.Major7), // IVmaj7 new Chord(new Note(NoteName.G, 4), ChordType.Dominant7), // V7 new Chord(new Note(NoteName.A, 4), ChordType.Minor7), // vi7 new Chord(new Note(NoteName.B, 4), ChordType.HalfDiminished7) // viiø7 };

Special Chord Types

Power Chords

var powerChord = new Chord(new Note(NoteName.E, 3), ChordType.Power); // Contains only root and fifth: E3, B3

Sixth Chords

var c6 = new Chord(new Note(NoteName.C, 4), ChordType.Major6); // C, E, G, A var cm6 = new Chord(new Note(NoteName.C, 4), ChordType.Minor6); // C, Eb, G, A

Altered Dominants

var alteredDominant = new Chord(new Note(NoteName.G, 4), ChordType.Dominant7Sharp5); // G, B, D#, F var jazzDominant = new Chord(new Note(NoteName.G, 4), ChordType.Dominant7Sharp11); // G, B, D, F, C#

Performance Notes

  • Chord note generation uses cached interval lookups

  • Symbol generation is optimized with switch expressions

  • GetNotes() yields notes lazily when possible

  • Transposition creates new instances (immutable)

Thread Safety

The Chord class is immutable and thread-safe. Multiple threads can safely:

  • Read all properties

  • Call all methods

  • Share Chord instances

No synchronization is needed.

Validation

  • Root note must not be null

  • ChordType must be a valid enum value

  • Invalid combinations are prevented at compile time through the type system

See Also

13 June 2025
Interval API ReferenceScale API Reference