Understanding how to recognize and use 7ths is a wonderful way to add dimension and texture to a piece of music. Let’s break down how to understand what an A7 is and how it differs from other similar looking chords.
An A7 chord is short for A dominant 7. The notes are A C# E and G. The first three notes (A C# and E) make up the triad A Major, and the G is the 7th that is added on to make it a dominant 7 chord. Its sound character is noted for having dissonance and instability that creates a tension.
What Does The 7 Mean In A7 Chord?
The 7th of A7 means that the flat 7th shall be added to the A Major triad. It is considered an extension of the root triad. It is called a dominant 7th because the 7ths exists naturally in the key it is the 5th, or dominant, of. So, for example, A7 is the 5th scale degree of D, and the G that makes the extension the 7th exists naturally in the key of D.
On piano, the A7 is typically played with the root note, A, being played as the lowest note in the sequence. It is possible to play a separate sequence order of the same notes, which is called an inversion. So, for example, one can play C# E G A from low note to high note, and it remains an intact A7 chord, as all four notes are present.
On guitar, the most common place to play an A7 would be to have all the strings open, except for the D and B strings, where one would play fret 2. Often, the lowest E string will not be strum during the performance of an A7 in this manner.
Is A7 Major Or Minor?
An A7 chord is Major.
In standard lead sheet nomenclature, the presence of only the capital letter for a note means major. In order to represent minor, a lowercase “m” would be added. This would be done before the extension, in this case the 7. So to write A minor 7, it would look like Am7.
Both the A7 and Am7 will add the G as the 7th extension, but the underlying triad will be different. In A7, the triad will be A major, and in Am7, the triad will be minor. The 7th may then be added to complete the chord.
Difference Between A7 and Amaj7
A7 is shorthand for “A Dominant 7,” while Amaj7 is shorthand for “A Major 7.” These two chords may look similar and have 3 of their 4 notes shared between them, but their sound characteristics sound very different from each other.
Amaj7 is made up of the notes A C# E and G#. This is because in order to make the Major 7 addition, we are adding the note that falls on the 7th scale degree of the A major scale. The A major scale is A B C# D E F# G# with the G# landing on the 7th degree, and therefore becoming the note we add to the A major triad to create an Amaj7.
From a sound perspective, A7 has a much more unstable and dissonant sound. Amaj7 has a much more open and lush sound. The A7 unstable sound comes from the present of a tritone interval, which is the interval between the C# and G. This interval, 6 semitones from each other, has been called “The Devil’s Interval” during religious dominated times in history, particularly during the Church’s dominance of music in the 17th and 18th century in Europe because of its harsh and clashing tone.
Amaj7, on the other hand, creates a smooth and atmospheric sound, used often to create lush arrangements and textures. This occurs because the space between each interval is greater, and even though there is a dissonant interval within the chord (The A and G#), they are a great enough distance away from each other to not have a “rub.”
What Are 7 Chords Used For?
7 chords are used to add more harmonic complexities and are added to triads. For more atmospheric and lush arrangements, a maj7 or m7 will be used. For more dissonant and unstable uses, a dominant 7, half diminished 7, fully diminished 7, minor major 7, or augmented 7th will be used.
The most common 7ths used are the dominant 7, the major 7, and the minor 7. The dominant 7 will be used to create tension, either to make a move to a new chord (often the major chord 7 semi-tones down), or to keep an unstable energy throughout a piece. A common use for dominant 7ths is in early rock n roll and blues, which give an edginess to the music.
The major and minor 7 are both used when a smoother texture is desired. Many ballads will employ the use of either major or minor 7ths (depending on if the underlying triad is major or minor) to give a bigger and more atmospheric sound to fill the space in arrangements. These chords can be heard in blues, folk, and jazz, among other genres.
Why Does Jazz Use 7th Chords?
Jazz uses 7th chords. The basis of jazz was to add complexity to existing music. Harmonically speaking, a great way to do this is to add extensions. Extensions are any notes added above the basic triad chord. The 7th is the most common extension as it continues the addition of adding thirds that the triad started, as shown in the figure below.
As you can see with all these chords, if you ignore the flat symbols, all the notes are neatly stacked in thirds, in this case every line on the staff. If you kept going and continued to add thirds, you would continue creating extensions such as 9ths, 11ths and 13th.
With jazz having so much emphasis on complexities, it makes sense that jazz would commonly use 7ths, and it is the first and most basic extension to add richness to triads. It also gives simpler instrumentation, such as a jazz trio with only bass, drums, and piano, a chance to sound bigger, as the extensions will thicken up the sound.