What are seventh chords? What are they used for? How can they be studied? In this lesson, we will try to answer these questions. In particular, we will look at what the harmonization of the major scale is, in order to discover the origin of chords.
Even those who do not play an instrument know that music is made up of scales and chords. The musical scale creates the melody, the horizontal dimension of music. The chord, on the other hand, develops the harmony, i.e. the vertical dimension, the superimposition of several sounds simultaneously.
According to the Garzanti music encyclopaedia, a chord is a simultaneous combination of several sounds. Wikipedia, on the other hand, describes a chord as a simultaneous combination of several sounds with a defined pitch. Before dealing with seventh chords, we will talk about triads, i.e. chords consisting of three notes.
Building triads with intervals
A musical chord requires three or more sounds. The superposition of just two sounds forms an incomplete chord, known as a bicord. Chords of three sounds are called triads. There are four different types of triads: major, minor, diminished and augmented.
Chords are made by superimposing the sounds of a scale in third intervals, i.e. by skipping a note. The interval of thirds can be major (when it is formed by four semitones, equal to two tones) or minor (when it is formed by three semitones, equal to a tone and a half).
- The major third is formed by two tones (four semitones)
- The minor triad is formed by a tone and a half (three semitones)
Combining two intervals results in a triad chord. There are four possible combinations:
- Major third + minor third = major triad
- Minor third + major third = minor triad
- Minor third + minor third = diminished triad
- Major third + major third = augmented triad
Here are the four types of triad starting with the note C, written on the staff.
In the first case, there are four semitones between C and E, and three semitones between E and G: it is therefore a major triad.
In the second case, between C and E♭ there are one and a half tones, between E♭ and G there are two tones. The intervals are arranged in exactly the opposite way to the major chord. The second chord in the example is therefore a minor triad.
In the third case we have two minor thirds, both between C and E♭ and between E♭ and G♭. We are dealing with a diminished triad.
The fourth and last case shows an augmented triad: between C and E there is a major third, and the same between C and G#.
Creating triad chords is therefore very easy by measuring the distance between the sounds of the triad: remember that there are only two possible intervals, the major third (which measures two tones, equal to four semitones) and the minor third (which measures one and a half tones, equal to three semitones).
To form seventh chords, however, it is better to use another system, called scale harmonization. In practice, instead of counting the various intervals as we did with the triads, we derive the chords from the major scale. Let’s see how.
Finding seventh chords from the scale
To find and learn quadriad chords, we start with the harmonization of the major scale. The major scale gives rise to four different types of chords, each of which can then take on four different forms, called inversions.
Scale harmonization is important not only for the chords it reveals, but also as a process in general, since chords can be made from any scale and the two dimensions – the horizontal or melodic and the vertical or harmonic – are always intimately connected. If you need a refresher, see the article on the origin and form of the major scale.
Seventh chords and major scale harmonization
The term “scale harmonization” refers to the construction of seventh chords from the notes contained in the scale itself. The process is simple: starting with each note of the scale (called a degree and indicated by Roman numerals), we superimpose a series of intervals of thirds. By superimposing the third note, the fifth note and the seventh note on the starting note (called root or fundamental), we obtain a four-part chord.
If we think of the notes of a scale lined up one after the other on a chessboard, the seventh chords are thus derived by jumping from a black square to a black square, or from a white square to a white square.
It is important to keep in mind that through the process called “scale harmonization”, chords are derived from the scale itself, so that all chords, no matter what degree they are built on, use only the notes of the starting scale.
Let’s now take a look at the harmonization of the major scale and the chords that are derived from it. We will take the C major scale as an example because it is the simplest, the one that uses no alterations. On the piano keyboard, it only consists of white keys.
The seventh chords we find through the harmonization of the major scale are of four types:
- On the I and IV degree we find the maj7 chord
- On the II, III and VI degree we find the m7 chord
- On the 5th degree we find the 7 chord
- On the 7th degree we find the m7♭5 chord.
It is very important to memorise this sequence, i.e. the position of the different chords on the various degrees of the major scale.
Quadriad inversions
By harmonising the major scale, we have found the seventh chords in their first position, known as the root position. The root is in fact the first note of the chord, the one from which the chord takes its name and on which the chord is built with the addition of thirds, fifths and sevenths.
Once you’ve learned how chords are made in their root position, you can deal with their secondary positions, known as inversions. A chord is said to be an inversion when the lowest note is not the root note but one of the other three notes:
If these concepts are too advanced for you, you may be interested in the Functional Harmony Video Course, to learn the most common chords, cadences and harmonic progressions.
Some exercises to learn chords
Let’s take a look at some exercises to learn how to quickly form seventh chords (also known as quadriads) in all keys.
- Build and play the maj7 chord in root position in all keys, following the circle of descending fifths: Cmaj7, Fmaj7, B♭maj7 etc.
- Build and play the 7 chord in root position in all keys, following the circle of descending fifths: C7, F7, B♭7 etc.
- Build and play the m7(♭5) chord in root position in all keys, following the circle of descending fifths: Cm7(♭5), Fm7(♭5), B♭m7(♭5), etc.
- Repeat the previous exercises 1-4, this time building and playing each chord in all its possible forms: root position and inversions
- Build and play the twelve harmonised major scales, finding the correct chord on each degree.
If you play a harmonic instrument (piano, guitar, etc.) play the arpeggio first, then the entire chord. The exercises are in progressive order of difficulty, so start with the maj7 chords and move on to the next ones only after you have mastered them well.
If you play a melodic instrument, play the notes one at a time, i.e. play the arpeggio of the chord. Even if you play a wind instrument, it is essential to know the notes that form the chords, especially if you want to learn to improvise.
A shortcut for finding the seventh of a chord
In the process called scale harmonisation, we discovered quadriad chords by deriving the third from the fundamental, the fifth from the third and the seventh from the fifth.
It’s a bit like building a four-storey building: in order to add the fourth floor, the seventh, the other three must be underneath: the first, third and fifth.
However, there is a shortcut to finding the seventh of a chord immediately. Analysing the chord Maj7 (the one we find on the I and IV degrees of the scale), we realise that the major seventh of the chord cannot grow any further: if we add a semitone to the seventh of the chord, we find the octave. On the other hand, the minor seventh is one tone away from the octave. This observation translates into a simple rule:
- To find the major seventh of any chord, simply go down a semitone. For example, the major seventh of B♭ is A natural (i.e. the note that is one semitone below B♭)
- To find the minor seventh of any chord, simply go down one tone. For example, the minor seventh of E♭ is D♭ (i.e. the note that is one tone below E♭)
This shortcut is particularly useful for calculating the major and minor sevenths of a chord regardless of whether it has an altered (diminished or augmented) fifth. In such cases, deriving the seventh from the fifth can lead to errors.
Finding the seventh with this system is a bit like getting to the fourth floor (the seventh) through the roof (the eighth) instead of walking up through the other three floors (root, third, fifth).
Other types of chords
To play most songs, triad and seventh chords are more than enough. Some musical genres, e.g. jazz, also employ far more complicated chords. Let’s take a few examples: the 9th,11th, 13th chords, or the quartal chords typical of modern jazz.
Chords with five or more voices: ninth,eleventh, thirteenth chords
In addition to triads and quadriads, there are also chords with five, six or seven notes. Just as we have reached the seventh of the chord, by superimposing intervals of thirds, we can go on to find a fifth voice of the chord (called the ninth), and again above the ninth we find the eleventh and finally the thirteenth.
When we consider chords with five or more voices, we speak of superior harmony or tensions. If we play all three voices of the upper harmony simultaneously, we get seven-voice chords.
Seven-tone chords are relatively rare, as not all notes of the scale can generate such complex chords. Examples of four- to seven-tone chords follow:
These chords sound much less consonant than triad chords, and are also more interesting than quadriad chords. Chords made up of several sounds are more interesting but also dissonant and more complicated to use.
This is why pop music uses mostly simple chords, some songwriters deliberately limit themselves to triad chords, so that the music sounds easy and predictable.
A system of symbols, which summarise the essential qualities of each chord, is used to write chords quickly. To find out more, see the lesson on how to read chord symbols.
Jazz chords: seventh chords and more
For some centuries, chords were made by superimposing notes at intervals of thirds. In the 20th century, chords made in other ways also came into use, such as superimposing fourths (example 1, below) or superimposing fourths and thirds together, such as the famous So What Chord invented by jazz pianist Bill Evans (example 2).
If these concepts are too advanced for you, you may be interested in the functional harmony course on this website. In particular, the third volume of the course is devoted to superior harmony and jazz chords.
In the course of the 20th century, a greater appreciation and interest in dissonance made it possible to start using very dissonant chords (example 3) and chord formations called clusters which, instead of spacing out sounds, use sounds very close to each other (example 4).
Conclusion: study harmony… to play better
Knowing at least the seventh chords perfectly is indispensable if you play a harmonic instrument such as the piano or guitar. Seventh chords are used to accompany, compose music and also to improvise. A serious study of harmony most definitely begins with knowledge of scales and chords.
If you would like more information and exercises for learning all types of chords, please see the harmony course and the improvisation course on this website. If you have any questions or additions to this lesson, please write a comment or question below. Thank you!