Major and minor chords differ only by half steps, making their calculation simple using the same formula used to find basic major chords.
As with major triads, minor chords follow the same formula. You start with the root note followed by major third, perfect fifth intervals and flattening major third to make minor. To create minor chords the letter ‘b’ must be added for flattening major third into minor third.
1. Root Note
Minor chords tend to have darker tones than major ones but still manage to sound highly consonant and stable, thanks to being formed from triads – an essential building block of tonal music.
A triad is composed of three notes, the root note (C) and two chord tones above it: E and G – its root being C with minor third above and perfect fifth above this minor third.
These intervals form the core of a chord, while its quality (major, minor or diminished) is determined by its key signature. Root note of key signature will define what chords can be built from it – perhaps adding extra tones like sevenths, ninths or augmented chords for more complex tones if desired.
2. Triad
A triad consists of three notes that are stacked one on top of another; its lowest note, known as the root, and two others – minor third and perfect fifth respectively.
These notes are separated by intervals; the minor third refers to the distance between the root and second note in a chord, and perfect fifth refers to that between second note and third note in a chord.
Each triad has its own distinct quality that is determined by the note interval properties of its roots and fifths, and may be major, minor, diminished or augmented.
To determine the quality of a triad, draw its root note onto a staff, followed by an outline resembling a snowperson with notes that form its minor third and perfect fifth above it. This will reveal its name along with any accidentals specific to your key signature.
3. Major Third
A Major Third is a musical interval composed of four half steps. When seen on Western staff notation, guitar frets or piano rolls, this represents two notes that are separated by three empty spaces (also called semitones).
These intervals when strung together form major chords. Additionally, they can also be combined with other intervals to form compound chords, like Minor Sixth.
Recognizing Major Thirds can aid a musician’s ability to recognize chord qualities in both compositions and improvisations, for instance when there’s a Major Third between root and third; such a chord will have an uplifting sound with bright tones that stand out.
Flattening a major third to create the Major Sixth interval can create an augmented fifth instead of diminished fifth depending on how it’s played in just intonation.
4. Minor Third
Minor thirds are an interval that consist of two notes that are one whole step and a half apart, as opposed to major thirds which consist of three whole steps.
As an easy way of remembering this concept, consider major chords and minor triads as intervals: major intervals consist of two semitones while minor intervals contain three semitones; thus if you played an interval in C major scale between C to E it would sound like a major chord while moving that interval down one note by adding A will create a minor chord.
So if you can grasp this concept, then you have some idea why a minor chord sounds melancholic while major chords bring joy. I urge you to spend the time to really learn this idea well; start practicing major and minor intervals until it becomes part of your music making experience.