The ToolKIT, which is accessible from all pages of the site, outlines the three main analytical skills that TonalityGUIDE.com aims to develop. It also links to a short introduction to the study of tonality as well as a reminder of some basics (note and interval labels, clefs and transpositions).
The triad, along with the scale, is one of the basic units of tonal music. It usually refers to a particular kind of three note chord that consists of two intervals of a third stacked one on top of the other.
The triad constructed from thirds is special because it is the only possible type of three-note chord that is completely consonant. Any other combination of intervals would include a dissonant interval of a second or seventh (or compound versions of these intervals).
The only other consonant three-note chords (i.e. triads containing a third or a fourth) are in fact inversions of triads constructed from thirds.
[many theorists have suggested that the triad is based on the harmonic series]
With two different types of third (major and minor) there are four possible permutations, as shown in the example below. How these function in the tonal system is the main subject of this web site, but it is generally true that major and minor triads are considered more stable in most tonal styles. Augmented and diminished triads usually resolve
to a major or minor triad and in some earlier styles only the major triad was considered stable enough to end a whole piece.
|lower third||upper third||name
Inversions of intervals
An interval is inverted by moving the bottom note of the interval up an octave so that it is above what was previously the top note. It is called an inversion because by putting the bottom note at the top, you are turning the interval upsidedown. The example below shows the common diatonic intervals and their inversions (click here to see the inversions of all the other various intervals):
Inversions of triads
Triads can be also be inverted by moving the bottom note up an octave. Because triads consist of three notes, they can be inverted twice as in the example below. The bottom note of a triad in its original position, arranged as a stack of two thirds, is called the root and so is said to to be in root position. The names for the two inversions speak for themselves:
The inversions of the C major triad can be rearranged without necessarily changing the inversion. For example, the first C major triad below is arranged so that the three notes are as close together as possible. A triad arranged arranged like this is said to be in 'close position'). In the second example below, the C major triad is is spread out but the root is still at the bottom. While it is still in root position it is now said to be in 'open position'.
In all these examples the notes of a C major triad have been re-arranged in various ways and while this considerably changes their sound, they are all recognisably C major triads. This is clear if you compare the sound of them as as group with, for example, a C augmented or E flat minor triad.
TIP: if you want to know if a three-note chord is based on a triad constructed from thirds, and which triad it is, you can try re-arranging it as a stack of thirds
The addition of a seventh above the root to a triad is so common that there is some justification for discussing these as chords in their own right.
Five different types of seventh chord can be constructed based on the diatonic triads of the major and minor scales with the addition of the seventh. These are shown in the example below, but the various types are discussed in more detail in the diatonic short progressions section.
The five types are:
You can find out the closest position (and therefore the root) of any chord by rearranging it as a stack of thirds. The following example shows a seventh chord in inversion and then rearranged in root and close position:
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© Copyright Thomas Pankhurst