A suspended chord is a chord in which the third is replaced or accompanied by either a fourth or a major second, although the fourth is far more common.
This type of sound is borrowed from the contrapuntal technique of suspension, where a note from a previous chord is carried over to the next chord, and then resolved down to the third or tonic, suspending a note from the previous chord. However, in a suspended chord the added tone does not necessarily resolve.
Suspended chords are most commonly found in folk music and popular music.
There are also a number of non-standard sixth chords. The added sixth chord, as the name suggests, is a triad with an added sixth. It is generally built on the sub-dominant (fourth scale degree), although they can be built on any note. An added sixth chord built on C consists of the notes C, E, G, and the added sixth A. These are the same notes as those of an A minor seventh chord - whether such a chord should be regarded as an added sixth chord or a seventh depends on its context and harmonic function.
The Neapolitan sixth is the first inversion of a major triad built on the flattened supertonic (second degree of the scale) - a Neapolitan sixth in C major, therefore, consists of the notes D flat, F and A flat. It being a first inversion explains the sixth part of its name; why the name makes reference to Naples is less clear, though it may be because the chord was particularly popular with composers of the so-called Neapolitan school of the 18th century. It often precedes a perfect cadence, when it functions as a sub-dominant.
There are a number of augmented sixth chords. Each of them have a major third and augmented sixth above the bass. When these are the only three notes present, the chord is an Italian sixth; when an augmented fourth is added above the bass, the chord is a French sixth; while adding a perfect fifth above the bass of an Italian sixth makes it a German sixth (the etymology of all these names is unclear). All usually have the flattened sub-mediant (sixth degree of the scale, A flat in C major, for example) as the bass note -in this case, they tend to resolve to the dominant.Suspended chords
Sixth Chords
Generally speaking, a sixth chord is any chord which contains the interval of a sixth. The simplest example is the first inversion of a triad, which consists of a third and a sixth above the root; when the term sixth chord is used without qualification, it usually refers to such a chord.