A chord progression with more than two chords of the same type is known as a constant structure in music. Because all of the chords are minor sevenths, a chord progression involving playing an A minor seventh chord, then a C minor seventh chord, then an E minor seventh chord, for example, follows a consistent structure. A pattern of the same types of chords is referred to as a constant structure, and the types of chords that can be used in this application are numerous. Though chords are essentially three or more notes played at the same time, there are many different types of chords.
Major and minor chords, as well as dominant and diminished chords, intervals, triads, and other chord types, can all be used for constant structure. A series of similar intervals played as chords would qualify as constant structure, even though a two-note chord is technically an interval and not a chord. Playing the root and sixth note for three or more consecutive root notes is an example of intervals played in constant structure.
Intervals are a way of indicating the location of notes in a chord in relation to its root when reading, writing, and learning music. The notes progress in the pattern of the chosen scale as you count intervals. Interval one refers to the root, or the lowest note in the scale. Interval two is the next note. The third interval, which helps define the common major triad chord, is a common participant in triads.
The terms used to describe chords aid in indicating the relative positions of its notes to the root note. The root, major third, and fifth are all included in a major seventh chord, as well as the major seventh interval, which is the note played just before reaching the octave root of the scale. Knowing the note pattern that makes up a chord can aid a composer in replicating the chord in a different root for a chord progression with a consistent structure.
The root note, the note one half-step below the third, and the fifth, which form a minor triad, are usually included in a minor seventh, along with the note one half-step below the major seventh of the scale. A minor-minor seventh is another name for this. A minor seventh chord, like the minor-minor seventh, contains the minor triad root, but it keeps the major seventh on top. A minor-major seventh is what this is called. Unstable chord progressions, such as the fourth and seventh, can help give a constant structure chord line a sense of tension, while resolving it to the root gives a sound of release or relaxation.