Tetrads
Four-note chords — triads with an added 7th
A tetrad is a four-note chord, formed by adding a 7th to a triad. Its type depends on the underlying triad and the size of that 7th.
NoSheet focuses on the three most common tetrads, which also arise naturally from the major modes:
- Major 7th — major triad plus major 7th. Dreamy and lush. Two per major mode.
- Dominant 7th — major triad plus minor 7th. Tense and bluesy, pulling toward the root. One per mode, and the only tetrad containing a tritone.
- Minor 7th — minor triad plus minor 7th. Mellow and jazzy. Three per mode, making it the most common type.
Each tetrad is built by the same rule as a triad: pick a note, skip the next, pick the following, and so on until you have four. As a result, every tetrad contains two of the mode's triads.