Triads

5.1 Definition

A triad, as the name implies ("tri" = three) is a structure built of three different notes.  Based on that definition, it is theoretically possible to build structures built on two, four, or even five notes (dyads, quadrads, and quintads), but the Western system relies very heavily on three-note verticalities.

5.2 Tertian harmony and triad nomenclature

The name "tertian" refers to the predominant intervals being used to build the vertical structure.  ("ter"=three).  Again, it is possible to use secundal (2nds), quartals (4ths), quintals (5ths), etc., but these are not common to traditional Western styles.

Therefore, a triad constructed using tertian harmony would be a three-note idea wherein all of the notes are a third apart from another, as in:

 

As you can see, the bottom note of the structure is named the "root," and the top note is named the "fifth." 

Triads may appear in either clef, of course, and may appear as line-line-line (as above) notes or space-space-space notes. 

5.1 The flexibility of triads

Believe it or not, most pieces of standard Western music (especially hymn harmonizations) use nothing more than simple triadsthree notes appearing at the same time.  If you understand the essentials of triad construction, you will have come a long way towards understand a large body of music.

One interesting feature is that no matter what octave the pitches of a triad appear in, they still retain some of the aural characteristics of the original triad.  Also, in this case, the root will always be known as the root, etc., regardless of what note actually appears at the bottom of the structure!

For example, the triad above (called an F major triad, since it uses scale degrees 1, 3, and 5 of the F major scale) could be spelled out any number of ways and still retain its F major triad characteristics:

 

Each one of the measures contains the pitches F, A, and C, and are therefore all considered F Major Triads, just as the first measure, and will sound, more or less, like the original triad (play these to hear this phenomenon).

 

Important Note : As mentioned in 5.2 (above), every triad has a root, a third, and a fifth.  The names for these pitches remain constant regardless of where they appear in pitch space.   In other words, the second and final measures in the example above both have the root appearing as the highest note (F) and the third appearing as the lowest (A).

It is critical to remember that when triads are "spread out" through the pitch space, they may not immediately appear to be triadic.  The third measure above does not look at all like a triad, because it has a fifth (from F-C) and a sixth (from C-A).  Once we "reduce" everything, however, we still have a triad F-A-C.  Therefore, get in the habit of "scrambling" pitches to see if they fit into a triadic form (thirds).

5.1 Doubling notes

Just as pitches can appear in various octaves and registers, they can be doubled without destroying the original quality of the triad.  This technique is used in four-part chorales (hymns) to take a three-note idea and use it with four separate voices:

 

Each one of the beats in the four-part piece above uses the notes F A and C.  On the first triad, note that the root is doubled (there are two instances of the root, one in the alto and the other in the bass.)  In the second triad, we find the fifth is doubled (tenor and bass), and in the third, we see the root doubled (soprano and alto), and so on.

A similar phenomenon happens in orchestral scores, where three notes (a triad) may be spelled out between many instruments with various pitches doubled.

A point to remember : Once again, recall that triads that do not appear to be spelled in thirds may still be triads after all! 

5.1 Omitted notes

Triads typically appear in their entirety, so it is a little unusual to encounter triads with missing notes (for then they are no longer triads).  Although you will learn, in later semesters, that there are occasions for leaving notes out of your triads, during the first three semester we will always make certain all three notes are present in any triad.

5.2 Triad qualities

In the same way intervals have qualities (see section 4.0 Intervals) triads do as well.  To correctly identify triads, it is necessary to have a very firm grasp of your interval spellings.

Here are some rules for identifying and spelling triads: