tertian

In music theory, tertian (, "of or concerning thirds") describes any piece, chord, counterpoint etc. constructed from the intervals of (major and minor) thirds. An interval such as that between the notes A and C encompasses 3 semitone intervals (A-B-B-C) and is termed a minor third while one such as that between C and E encompasses 4 semitones (C-D-D-E-E) and is called a major third. Tertian harmony (also called tertiary harmony) principally uses chords based on thirds; the term is typically used to contrast with quartal and quintal harmony which uses chords based on fourths or fifths.