tertian

a tertian chord progression in the minor (i-v-i-iv-i-v-I) ending on a Picardy third play (help·info)

Look up tertian in Wiktionary, the free dictionary.

"Tertial" redirects here. For the feathers in a bird's wing see tertials.

The word tertian, deriving from the Latin word tertianus, means "of or concerning thirds". In medicine it is used to denote "cycles of the third day", speaking inclusively, thus applying, for example, to diseases that show a recurring 48-hour pattern (such as tertian ague, tertian malaria).^[1]

In music theory "tertian" describes any piece, chord, counterpoint etc. constructed from the interval of a third. An interval such as that between the notes A and C encompasses 3 semitone intervals (A-Bflat-B-C) and is termed a minor third while one such as that between C and E encompasses 4 semitones (C-Dflat-D-Eflat-E) and is called a major third (See Major and minor).

A common triad chord can be regarded as consisting of a "stack" of two such intervals. A musical scale may also be analysed as a succession of thirds (See Ladder of thirds). The meantone temperament, a system of tuning that emphasises pure thirds, may be called "tertian".

Chords built from sixths may also be referred to as tertian because an ascending sixth is equal to a descending third and vice versa: any sixth can be taken as the inversion of a third. For instance the interval C-A is a major sixth that, when inverted, gives the interval A-C, which is a minor third.

Tertian concepts have been used innovatively in chord progressions, as for example in the "thirds cycle" used by John Coltrane (see Coltrane changes).

References

See also

• Secundal
• Quartal and quintal harmony
• Polychord

External links

• Definition of tertian in the Merriam-Webster Online Dictionary
• Definition of tertian at dictionary.com

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