Seconds
When you arrange the seven natural notes in the order of fourths beginning on B, you get B–E–A–D–G–C–F. From the first two letters (B and E), the resulting pairs B–C and E–F form minor seconds. All the remaining pairs (A–B, D–E, G–A, C–D, and F–G) form major seconds.
In the table below, notice how the top and bottom notes of each column also follow the order of fourths.
Minor Seconds Major Seconds Major Seconds Major Seconds Minor Seconds Minor Seconds
B-C B-C# B♭-C A-B A-B♭ A#-B
E-F E-F# E♭-F D-E D-E♭ D#-E
G-A G-A♭ G#-A
C-D C-D♭ C#-D
F-G F-G♭ F#-G
You can alter the naturally minor seconds (B–C and E–F) into major seconds by either flatting the first note or sharping the second, changing the distance from one half-step to two.
Likewise, naturally major seconds (A–B, D–E, G–A, C–D, F–G) can become minor seconds when the first note is sharped or the second is flatted, reducing the distance from two half-steps to one.
This same pattern of alteration applies to all major/minor interval types.
Thirds
Take a look at thirds:
Minor Thirds Major Thirds Major Thirds Major Thirds Minor Thirds Minor Thirds
B-D B-D# B♭-D G-B G-B♭ G#-B
E-G E-G# E♭-G C-E C-E♭ C#-E
A-C A-C# A♭-C F-A F-A♭ F#-A
D-F D-F# D♭-F
If you flat the first note or sharp the second in a minor third, it becomes a major third (increasing from three to four half-steps). Conversely, flatting the second or sharping the first in a major third changes it back to minor (reducing from four to three half-steps).
The same logic applies to sixths:
Minor Sixths Major Sixths Major Sixths Major Sixths Minor Sixths Minor Sixths
B-G B-G# B♭-G D-B D-B♭ D#-B
E-C E-C# E♭-C G-E G-E♭ G#-E
A-F A-F# A♭-F C-A C-A♭ C#-A
F-D F-D♭ F#-D
Flat the first note or sharp the second in a minor sixth and it becomes a major sixth (eight to nine half-steps). Reverse the alteration and the major sixth becomes minor (nine to eight half-steps).
Sevenths
And the same with sevenths:
Minor Sevenths Major Sevenths Major Sevenths Major Sevenths Minor Sevenths Minor Sevenths
B-A B-A# B♭-A C-B C-B♭ C#-B
E-D E-D# E♭-D F-E F-E♭ F#-E
A-G A-G# A♭-G
D-C D-C# D♭-C
G-F G-F# G♭-F
Flat the first note or sharp the second in a minor seventh to make it major (ten to eleven half-steps). Sharp the first or flat the second in a major seventh to make it minor (eleven to ten half-steps).
Fourths
With fourths and fifths, the pattern changes slightly because these intervals are classified as perfect, augmented, or diminished rather than major or minor.
Perfect Fourths Dim. Fourths Aug. Fourths Perfect Fourths Aug. Fourths
B-E B-E♭ B-E# F-B♭ F-B
E-A E-A♭ E-A# F#-B
A-D A-D♭ A-D#
D-G D-G♭ D-G#
G-C G-C♭ G-C#
C-F C-F♭ C-F#
For fourths, sharping the first note or flatting the second turns a perfect fourth into a diminished fourth (five to four half-steps). Sharping the second note turns it into an augmented fourth (five to six half-steps).
Fifths
The same applies to fifths:
Perfect Fifths Dim. Fifths Aug. Fifths Dim. Fifth Perfect Fifth
E-B E-B♭ E-B# B-F B-F#
A-E A-E♭ A-E#
D-A D-A♭ D-A#
G-D G-D♭ G-D#
C-G C-G♭ C-G#
F-C F-C♭ F-C#
Sharping the first note or flatting the second produces a diminished fifth (seven to six half-steps). Sharping the second note produces an augmented fifth (seven to eight half-steps).
Narrowed by one half-step ←Original Interval→ Widened by one half-step
Minor Major Augmented
Diminished Minor Major
Diminished Perfect Augmented
While these charts make look extensive, they do not list every interval. Using your understanding of altered scale degrees, you can transform any interval’s quality:
· Major ↔ Minor
· Perfect ↔ Diminished or Augmented
This logic reveals how interval quality changes mathematically—allowing you to see every relationship on the fretboard clearly and precisely.