Working with Notes

The Note class is the fundamental building block of the MusicTheory library. It represents a musical pitch with a specific name, alteration, and octave.

Understanding Notes

A note in music theory consists of three components:

Note Name: One of the seven natural notes: C, D, E, F, G, A, B
Alteration: Modifies the pitch: Double Flat (♭♭), Flat (♭), Natural (♮), Sharp (♯), Double Sharp (♯♯)
Octave: The register of the note, following scientific pitch notation (Middle C = C4)

Creating Notes

Using the Constructor

The most explicit way to create a note:

// Natural notes
var c4 = new Note(NoteName.C, Alteration.Natural, 4);
var a3 = new Note(NoteName.A, Alteration.Natural, 3);

// Altered notes
var fSharp5 = new Note(NoteName.F, Alteration.Sharp, 5);
var bFlat2 = new Note(NoteName.B, Alteration.Flat, 2);
var gDoubleSharp = new Note(NoteName.G, Alteration.DoubleSharp, 4);

// Simplified constructor for natural notes
var d4 = new Note(NoteName.D); // Defaults to natural, octave 4
var e5 = new Note(NoteName.E, octave: 5);

Parsing from String

Parse notes from standard notation:

// Basic notation
var c4 = Note.Parse("C4");
var fSharp5 = Note.Parse("F#5");
var bFlat3 = Note.Parse("Bb3");

// Double alterations
var fDoubleSharp = Note.Parse("F##4");
var bDoubleFlat = Note.Parse("Bbb2");

// The parser is case-insensitive
var note = Note.Parse("c#4"); // Same as C#4

From MIDI Numbers

Convert MIDI note numbers to Note objects:

// Middle C (MIDI 60)
var middleC = Note.FromMidiNumber(60);

// A440 (MIDI 69)
var a440 = Note.FromMidiNumber(69);

// Prefer flats for black keys
var db4 = Note.FromMidiNumber(61, preferFlats: true); // Db4 instead of C#4
var eb4 = Note.FromMidiNumber(63, preferFlats: true); // Eb4 instead of D#4

Note Properties

Basic Properties

var fSharp4 = new Note(NoteName.F, Alteration.Sharp, 4);

// Access components
NoteName name = fSharp4.Name;           // NoteName.F
Alteration alt = fSharp4.Alteration;    // Alteration.Sharp
int octave = fSharp4.Octave;           // 4

// String representation
string str = fSharp4.ToString();        // "F#4"

Calculated Properties

var a4 = new Note(NoteName.A, Alteration.Natural, 4);

// Frequency calculation (A4 = 440 Hz standard)
double freq = a4.Frequency;             // 440.0 Hz

// MIDI number
int midi = a4.MidiNumber;               // 69

// Total semitones from C0
int semitones = a4.GetTotalSemitones(); // 57

Note Operations

Transposition

Transpose notes by intervals or semitones:

var c4 = new Note(NoteName.C, Alteration.Natural, 4);

// Transpose by interval
var g4 = c4.Transpose(new Interval(IntervalQuality.Perfect, 5), Direction.Up);
var f3 = c4.Transpose(new Interval(IntervalQuality.Perfect, 5), Direction.Down);

// Common intervals
var majorThird = new Interval(IntervalQuality.Major, 3);
var e4 = c4.Transpose(majorThird); // Defaults to Up

var minorSixth = new Interval(IntervalQuality.Minor, 6);
var ab4 = c4.Transpose(minorSixth, Direction.Up);

var c4 = new Note(NoteName.C, Alteration.Natural, 4);

// Transpose by semitones
var d4 = c4.TransposeBySemitones(2);   // Up 2 semitones
var bb3 = c4.TransposeBySemitones(-2); // Down 2 semitones

// Octave transposition
var c5 = c4.TransposeBySemitones(12);  // Up one octave
var c3 = c4.TransposeBySemitones(-12); // Down one octave

Enharmonic Equivalents

Get enharmonically equivalent notes (same pitch, different spelling):

var cSharp = new Note(NoteName.C, Alteration.Sharp, 4);
var dFlat = cSharp.GetEnharmonicEquivalent(); // Db4

var e = new Note(NoteName.E, Alteration.Natural, 4);
var fFlat = e.GetEnharmonicEquivalent(); // Fb4

var gDoubleSharp = new Note(NoteName.G, Alteration.DoubleSharp, 4);
var a = gDoubleSharp.GetEnharmonicEquivalent(); // A4

// Check if two notes are enharmonic
bool areEnharmonic = cSharp.IsEnharmonicWith(dFlat); // true

Frequency and Tuning

The library uses A4 = 440 Hz as the standard tuning reference:

// Standard frequencies
var a4 = new Note(NoteName.A, Alteration.Natural, 4);
Console.WriteLine(a4.Frequency); // 440.0 Hz

var c4 = new Note(NoteName.C, Alteration.Natural, 4);
Console.WriteLine(c4.Frequency); // 261.63 Hz

// Frequency calculation follows equal temperament
var cSharp4 = new Note(NoteName.C, Alteration.Sharp, 4);
Console.WriteLine(cSharp4.Frequency); // 277.18 Hz

Common Patterns

Note Comparison

Notes can be compared for ordering:

var c4 = new Note(NoteName.C, Alteration.Natural, 4);
var g4 = new Note(NoteName.G, Alteration.Natural, 4);
var c5 = new Note(NoteName.C, Alteration.Natural, 5);

// Comparison
bool isLower = c4.CompareTo(g4) < 0;  // true
bool isHigher = c5.CompareTo(c4) > 0; // true

// Sorting
var notes = new[] { g4, c5, c4 };
Array.Sort(notes); // c4, g4, c5

Note Validation

Check if note properties are valid:

try
{
    // This will throw - MIDI range is 0-127
    var tooHigh = new Note(NoteName.C, Alteration.Natural, 10);
    int midi = tooHigh.MidiNumber; // Throws InvalidOperationException
}
catch (InvalidOperationException ex)
{
    Console.WriteLine(ex.Message);
}

// Parsing validation
if (Note.TryParse("C#4", out var note))
{
    Console.WriteLine($"Parsed: {note}");
}
else
{
    Console.WriteLine("Invalid note string");
}

Working with Note Collections

Common operations with multiple notes:

// Create a chromatic scale
var chromaticScale = new List<Note>();
var c4 = new Note(NoteName.C, Alteration.Natural, 4);
for (int i = 0; i < 12; i++)
{
    chromaticScale.Add(c4.TransposeBySemitones(i));
}

// Find interval between notes
var e4 = new Note(NoteName.E, Alteration.Natural, 4);
var interval = Interval.Between(c4, e4); // Major third

// Check octave relationships
var c5 = new Note(NoteName.C, Alteration.Natural, 5);
bool isSameNoteClass = c4.Name == c5.Name; // true
int octaveDifference = c5.Octave - c4.Octave; // 1

Advanced Topics

Enharmonic Spelling

Understanding when to use sharps vs flats:

// In the key of G major, use F# not Gb
var gMajorScale = new Scale(new Note(NoteName.G), ScaleType.Major);
var seventhDegree = gMajorScale.GetNotes().ElementAt(6); // F#4

// In the key of F major, use Bb not A#
var fMajorScale = new Scale(new Note(NoteName.F), ScaleType.Major);
var fourthDegree = fMajorScale.GetNotes().ElementAt(3); // Bb4

Octave Designation

The library follows scientific pitch notation:

C-1 to B-1: Sub-contra octave (MIDI 0-11)
C0 to B0: Contra octave (MIDI 12-23)
C1 to B1: Great octave (MIDI 24-35)
C2 to B2: Small octave (MIDI 36-47)
C3 to B3: One-line octave (MIDI 48-59)
C4 to B4: Two-line octave (Middle C) (MIDI 60-71)
C5 to B5: Three-line octave (MIDI 72-83)
C6 to B6: Four-line octave (MIDI 84-95)
C7 to B7: Five-line octave (MIDI 96-107)
C8 to B8: Six-line octave (MIDI 108-119)
C9 to G9: Seven-line octave (MIDI 120-127)

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