Triad
A triad is a chord of three pitch classes.
Quality
- See also: Category:Triads
Triads can be classified by quality, based on the quality of the intervals above their root.
Tertian triads
Many triads in Western classical music are based on tertian harmony, i.e. stacks of thirds. These triads occur naturally in the diatonic scale by taking the third and the fifth above the root, with different notes of the scale leading to different qualities.
The most common triads in modern music are the major triad (root-M3-P5) and the minor triad (root-m3-P5). Also common are the augmented triad (root-M3-A5) and the diminished triad (root-m3-d5). Note that the augmented triad does not occur naturally in the diatonic scale, except if you count the harmonic minor scale and the harmonic major scale (which are both altered diatonic scales).
Suspended second and suspended fourth triads may be classified as tertian triads if they are used, as their name implies, as suspensions leading to other tertian triads. They may otherwise be classified as quartal or quintal triads, depending on their voicing, if they are used differently, such as a set of parallel suspended triads.
The Perfect Triad (Claudi Meneghin), illustrates the spectrum of "perfect triads" in which the root and the 5th are fixed (at 2:3) and the third of the triad gradually moves through a spectrum of Just intonation intervals from subminor 7/6 to supermajor 9/7.
It should be noted that triads framed by a perfect fifth- or, rather, as many of such as were known in the Medieval era- were referred to under the term "quinta fissa" or "split fifth" by Jacobus of Liege[1]. Today, such a term could conceivably refer not only to Claudi Meneghin's "perfect triads", but also to suspended second and suspended fourth triads, and even other such triads that could be viable for voice-leading.
Xenharmonic triads
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In addition to the tertian and split fifth triads which are framed by the 3/2 perfect fifth, one could argue that there are other triads that could be referred to under the term "quarta fissa" or "split fourth". Such triads can be stacked multiple times in the span of a single octave due to two stacked instances of 4/3 being able to fit within the span of the octave. Because the perfect fourth sounds more alien than the perfect fifth as an interval for framing chords, chords formed this way only dial the strangeness up a notch when the divisions are of such sizes as to not cause crowding, and such triads are arguably xenharmonic.
See also
External links
References
- ↑ Speculum Musicae, c. 1325
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