As you become more acquainted with chords, you may come across conversations regarding major and minor keys. Music written in a minor key still uses all the same notes but has a unique scale pattern compared to that in major keys.
These differences cause chords to sound differently as well, as we can observe by counting the half steps between notes.
Triads
As discussed in our last lesson, triads consist of three notes, and can either be major or minor in nature with any interval between them.
Any note in a scale may serve as the root of a chord. Chords built on do, fa, sol (1, 4, 5) in major keys are known as major chords and indicated with capital letters; those built using re and mi (2, 3, 6); however; are minor triads indicated by lowercase letters while diminished quality triads built using ti (7,9) are indicated with superscript degrees.
With respect to octave equivalence, doubled or spread-out chord notes do not alter their identification; so that even when doubled or spaced out differently than intended, their identification remains unchanged – thus, for instance, a C minor triad in closed spacing can still be recognized as C minor chord and another identified with open spacing as C minor chord. Their identity also depends on bass voice position; these different inversions of chords are known by various names such as root inversion or first/second inversion respectively.
Dominant Sevenths
When a major triad is constructed with an added seventh note, it becomes known as a dominant seventh chord. This seventh note destabilizes the triad’s structure, making its sound more “dominant” while strengthening its tendency to move towards tonicity.
Minor scale chords often refer to themselves as altered dominant, since their fifth is moved down by one semitone, giving an increased dissonant feel and also creating an unusual tritone interval that usually remains absent in diatonic harmony.
To create a dominant seventh chord, start with a major triad and add its fifth and seventh notes – creating an E minor triad and then adding its minor seventh note, D, will result in an altered C dominant seventh chord. To help remember this equation simply think: Major Triad + 3 = Dominant Seventh
Sustained Sevenths
Minor major seventh chords in minor scale can be associated with any three chords that harmonize with its dominant 7th note or any chords with five notes, though their quality depends on its interval between its third and seventh tones, which classify as tertian harmony.
Seventh chords composed of me and le (|3 and |6) contain a minor triad and major seventh, while those constructed using do and re with raised leading tone (1 and 4) contain a diminished triad and diminished seventh; those constructed on ti (7) produce fully diminished sevenths.
These chords can create tension or bridge the transitions between chords, such as in The Beach Boys’ “God Only Knows.” You can also hear this effect in Bellini’s La Straniera where two adjacent iv and vi chords are prepared then resolved half step apart to give their characteristic tension.
Minor Sevenths
As we saw in our previous lesson, triad chords can be identified by their root notes. When adding a seventh interval above that root note of a triad, we have created a seventh chord; for instance, when added a major seventh interval above it we get Cmaj7 chord (or simply Maj7) chord.
Minor sevenths are built the same way as major sevenths; however, their tonal function differs slightly; they can serve as both major key and minor key fourth, fifth, sixth, seventh chords iv, vi and V chords as well as ii and iiiii chords respectively.
Understanding the underlying scales for each chord is crucial not only in terms of knowing its individual notes but also how they function within a key center. For instance, in Rhythm Changes and All The Things You Are the minor seventh functions as both an I and III chord in either major or minor keys.