Chord made of a tertian triad and a miscellaneous fourth note
C Suspended chord (sus2) and C added tone chord (add2). Both have the non-triad tone D, but are distinguished by the presence or absence of the third (E♭).[1]Ninth (C9) vs added-ninth chord (Cadd9), distinguished by the presence or absence of a seventh.[2]Playⓘ
An added tone chord, or added note chord, is a non-tertianchord composed of a triad and an extra "added" note. Any tone that is not a seventh factor is commonly categorized as an added tone. It can be outside the tertian sequence of ascending thirds from the root, such as the added sixth or fourth, or it can be in a chord that doesn't consist of a continuous stack of thirds, such as the added thirteenth (six thirds from the root, but the chord doesn't have the previous tertian notes – the seventh, ninth or eleventh). The concept of added tones is convenient in that all notes may be related to familiar chords.[3]
Inversions of added tone chords where the added tone is the bass note are usually simply notated as slash chords instead of added-tone chords. For example, instead of Cadd2/D, just C/D is used.
An added tone such as fourth voiced below the root may suggest polytonality.[4] The practice of adding tones may have led to superimposing chords and tonalities, though added tone chords have most often been used as more intense substitutes for traditional chords.[3] For instance a minor chord that includes a major second factor holds a great deal more dramatic tension due to the very close interval between the major second and minor third.[citation needed]Igor Stravinsky's polytonal Symphony of Psalms contains many added tone chords.[4]
A mixed third chord, also split-third chord,[6] includes both the major and minor thirds (e.g. C–E♭–E♮–G), although the thirds are usually separated by an octave or more.[4] A minor chord above a major chord of the same root has a diminished octave (major seventh) separating the thirds and is more common, while a major chord above a minor chord of the same root has a very dissonant augmented octave (minor ninth) separating the thirds and is not as commonplace. Paul McCartney's "Maybe I'm Amazed" is an example of the use of a split-third chord,[5] as are many of William Schuman's symphonies.[4] It is also suggested by the final note and chord of "A Hard Day's Night".[5]
The added-fourth chord (notated "add4") almost always occurs on the fifth scale degree where the added note is the key's tonic note. Examples in popular music include the second chord in the verse of "Runaway Train" and the introduction of The Who's "Baba O'Riley".[2]