Note API Reference

Complete API documentation for the Note class.

Class Definition

namespace MusicTheory;

public sealed class Note : IEquatable<Note>
{
    public NoteName Name { get; }
    public Alteration Alteration { get; }
    public int Octave { get; }
    public double Frequency { get; }
    public int MidiNumber { get; }
    public int SemitonesFromC { get; }
}

Constructors

Note(NoteName, Alteration, int)

Creates a new note with the specified name, alteration, and octave.

public Note(NoteName name, Alteration alteration, int octave)

Parameters:

name: The note name (C through B)
alteration: The alteration (double flat through double sharp)
octave: The octave number (-1 to 10)

Exceptions:

ArgumentOutOfRangeException: If octave is outside valid range

Example:

var cSharp4 = new Note(NoteName.C, Alteration.Sharp, 4);
var bFlat3 = new Note(NoteName.B, Alteration.Flat, 3);

Note(NoteName, int)

Creates a new natural note (convenience constructor).

public Note(NoteName name, int octave)

Example:

var c4 = new Note(NoteName.C, 4); // C natural

Properties

Name

public NoteName Name { get; }

Gets the note name (C, D, E, F, G, A, or B).

Alteration

public Alteration Alteration { get; }

Gets the alteration (DoubleFlat, Flat, Natural, Sharp, or DoubleSharp).

Octave

public int Octave { get; }

Gets the octave number. Middle C is in octave 4.

Frequency

public double Frequency { get; }

Gets the frequency in Hz using equal temperament tuning (A4 = 440 Hz).

Calculation:

frequency = 440 * Math.Pow(2, (semitonesFromA4 / 12.0))

MidiNumber

public int MidiNumber { get; }

Gets the MIDI note number (0-127). Middle C (C4) = 60.

Exceptions:

InvalidOperationException: If the note is outside MIDI range

SemitonesFromC

public int SemitonesFromC { get; }

Gets the number of semitones from C in the same octave.

Instance Methods

Transpose(Interval, Direction?)

Transposes the note by the specified interval.

public Note 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 Note instance

Example:

var c4 = new Note(NoteName.C, 4);
var g4 = c4.Transpose(new Interval(IntervalQuality.Perfect, 5));
var f3 = c4.Transpose(new Interval(IntervalQuality.Perfect, 5), Direction.Down);

TransposeBySemitones(int)

Transposes the note by a number of semitones.

public Note TransposeBySemitones(int semitones)

Parameters:

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

Returns: A new Note instance

Example:

var c4 = new Note(NoteName.C, 4);
var cSharp4 = c4.TransposeBySemitones(1);
var b3 = c4.TransposeBySemitones(-1);

IsEnharmonicWith(Note)

Determines if this note is enharmonically equivalent to another.

public bool IsEnharmonicWith(Note other)

Parameters:

other: The note to compare with

Returns: True if the notes have the same pitch

Example:

var cSharp = new Note(NoteName.C, Alteration.Sharp, 4);
var dFlat = new Note(NoteName.D, Alteration.Flat, 4);
bool same = cSharp.IsEnharmonicWith(dFlat); // true

GetEnharmonicEquivalent()

Gets the enharmonic equivalent of this note.

public Note? GetEnharmonicEquivalent()

Returns: The enharmonic equivalent, or null if none exists

Example:

var cSharp = new Note(NoteName.C, Alteration.Sharp, 4);
var dFlat = cSharp.GetEnharmonicEquivalent(); // D♭4

ToString()

Returns a string representation of the note.

public override string ToString()

Format: {NoteName}{Alteration}{Octave}

Examples:

C4 → "C4"
C#4 → "C#4"
Bb3 → "Bb3"
F##5 → "F##5"

Equals(Note?)

Determines if this note equals another note.

public bool Equals(Note? other)

Note: Compares by value (name, alteration, octave), not by enharmonic equivalence.

GetHashCode()

Returns the hash code for the note.

public override int GetHashCode()

Static Methods

FromMidiNumber(int, bool)

Creates a note from a MIDI number.

public static Note FromMidiNumber(int midiNumber, bool preferFlats = false)

Parameters:

midiNumber: The MIDI number (0-127)
preferFlats: Whether to prefer flats for black keys

Returns: A new Note instance

Exceptions:

ArgumentOutOfRangeException: If MIDI number is outside 0-127

Example:

var middleC = Note.FromMidiNumber(60);        // C4
var cSharp = Note.FromMidiNumber(61);         // C#4
var dFlat = Note.FromMidiNumber(61, true);    // Db4

TryParse(string, out Note?)

Tries to parse a note from a string.

public static bool TryParse(string input, out Note? note)

Parameters:

input: String representation (e.g., "C4", "F#5", "Bb3")
note: The parsed note, or null if parsing fails

Returns: True if parsing succeeded

Supported formats:

Natural: "C4", "D5"
Sharp: "C#4", "F#5"
Flat: "Bb3", "Eb4"
Double sharp: "F##5", "C##4"
Double flat: "Bbb3", "Abb4"

Example:

if (Note.TryParse("C#4", out var note))
{
    Console.WriteLine(note.Frequency); // 277.18
}

Operators

Equality Operators

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

Compare notes by value (not enharmonic equivalence).

Example:

var c1 = new Note(NoteName.C, 4);
var c2 = new Note(NoteName.C, 4);
var cSharp = new Note(NoteName.C, Alteration.Sharp, 4);

bool equal1 = c1 == c2;      // true
bool equal2 = c1 == cSharp;  // false

Constants and Limits

Octave Range

Minimum: -1
Maximum: 10

MIDI Range

Minimum: 0 (C-1)
Maximum: 127 (G9)

Frequency Range

Lowest: ~8.18 Hz (C-1)
Highest: ~12543.85 Hz (G9)
Reference: A4 = 440 Hz

Common Patterns

Creating Common Notes

// Middle C
var middleC = new Note(NoteName.C, 4);

// A440 (tuning reference)
var a440 = new Note(NoteName.A, 4);

// Black keys
var cSharp = new Note(NoteName.C, Alteration.Sharp, 4);
var dFlat = new Note(NoteName.D, Alteration.Flat, 4);

Working with Collections

// Create chromatic scale
var chromaticScale = Enumerable.Range(60, 13)
    .Select(midi => Note.FromMidiNumber(midi))
    .ToList();

// Sort notes by pitch
var notes = new List<Note> { /* ... */ };
var sorted = notes.OrderBy(n => n.MidiNumber).ToList();

Enharmonic Handling

public Note GetPreferredSpelling(Note note, KeySignature key)
{
    // Check if note fits the key
    if (key.GetAlteration(note.Name) == note.Alteration)
        return note;
    
    // Try enharmonic equivalent
    var enharmonic = note.GetEnharmonicEquivalent();
    if (enharmonic != null && 
        key.GetAlteration(enharmonic.Name) == enharmonic.Alteration)
        return enharmonic;
    
    return note; // Return original if no better spelling
}

Performance Notes

Frequency calculation is cached after first access
MIDI number calculation is performed on construction
Enharmonic lookups use efficient switch expressions
String parsing uses optimized character processing

Thread Safety

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

Read all properties
Call all methods
Share Note instances

No synchronization is needed.

MusicTheory Help

Note API Reference

Class Definition

Constructors

Note(NoteName, Alteration, int)

Note(NoteName, int)

Properties

Name

Alteration

Octave

Frequency

MidiNumber

SemitonesFromC

Instance Methods

Transpose(Interval, Direction?)

TransposeBySemitones(int)

IsEnharmonicWith(Note)

GetEnharmonicEquivalent()

ToString()

Equals(Note?)

GetHashCode()

Static Methods

FromMidiNumber(int, bool)

TryParse(string, out Note?)

Operators

Equality Operators

Constants and Limits

Octave Range

MIDI Range

Frequency Range

Common Patterns

Creating Common Notes

Working with Collections

Enharmonic Handling

Performance Notes

Thread Safety

See Also