Key signatures are musical shorthand, telling us which notes to play sharp or flat throughout a piece. They're like a code at the start of the staff, saving time and making music easier to read. Without them, we'd have to mark every single sharp or flat individually!

Understanding key signatures is crucial for reading and writing music in different keys. They help maintain the whole-half step pattern of major scales, ensuring the right intervals between notes. Mastering key signatures opens up a world of musical possibilities!

Key signatures for major keys

Understanding key signatures

• Key signatures are a set of sharps or flats placed at the beginning of a musical staff
  • Indicate which notes should be played as sharps or flats throughout the piece unless otherwise noted
• The key of C major has no sharps or flats in its key signature

Order of sharps and flats in key signatures

• The order of sharps in key signatures is F♯, C♯, G♯, D♯, A♯, E♯, B♯
  • Can be remembered using the mnemonic "Father Charles Goes Down And Ends Battle"
• The order of flats in key signatures is B♭, E♭, A♭, D♭, G♭, C♭, F♭
  • Can be remembered using the mnemonic "Battle Ends And Down Goes Charles' Father"
• Sharp key signatures are built by adding sharps in the order of the "sharp" mnemonic
  • Each new sharp is added to the right of the previous ones
• Flat key signatures are built by adding flats in the order of the "flat" mnemonic
  • Each new flat is added to the right of the previous ones

Writing major scales

Constructing major scales using key signatures

• Major scales are built using a specific pattern of whole steps (W) and half steps (H): W-W-H-W-W-W-H
• The key signature provides the sharps or flats needed to maintain the whole-half step pattern when writing a major scale
  • Key signature is placed at the beginning of the staff
  • All notes corresponding to the sharps or flats in the key signature are played as such throughout the scale, unless a natural sign (♮) is used
• If a major scale requires a sharp or flat that is not in the key signature, an accidental (sharp, flat, or natural sign) is placed directly before the affected note on the staff

Applying key signatures to major scales

• The key signature determines which notes need to be altered (sharpened or flattened) to maintain proper intervals between scale degrees in a given major key
• The key signature affects all octaves of the notes it contains, not just specific pitches within one octave of the scale
  • For example, in the key of G major (one sharp, F♯), all F notes in the scale, regardless of octave, are played as F♯

Key signatures and scale degrees

Understanding scale degrees

• Scale degrees are the names given to each note in a scale
  • Typically use numbers (e.g., 1, 2, 3) or solfège syllables (e.g., do, re, mi)
• In a major scale, the scale degrees are:
  • 1 (tonic)
  • 2 (supertonic)
  • 3 (mediant)
  • 4 (subdominant)
  • 5 (dominant)
  • 6 (submediant)
  • 7 (leading tone)
  • 8 (octave)

Relationship between key signatures and scale degrees

• Key signatures determine which notes need to be altered (sharpened or flattened) to maintain proper intervals between scale degrees in a given major key
  • For example, in the key of D major (two sharps, F♯ and C♯), the F♯ ensures that the interval between scale degrees 3 and 4 is a whole step, while the C♯ ensures that the interval between scale degrees 7 and 8 is a half step
• Key signatures affect all octaves of the notes they contain, not just specific pitches within one octave of the scale

Identifying major keys from signatures

Identifying major keys from sharp key signatures

• To identify the major key from a sharp key signature, locate the last sharp in the key signature and move up one half step (semitone)
  • This note is the tonic (first degree) of the major key
  • For example, a key signature with three sharps (F♯, C♯, and G♯) represents the key of A major

Identifying major keys from flat key signatures

• To identify the major key from a flat key signature, locate the second-to-last flat in the key signature
  • This note is the tonic (first degree) of the major key
  • For example, a key signature with two flats (B♭ and E♭) represents the key of B♭ major
• The key of C major has an empty key signature (no sharps or flats)