New JGT Lesson: Intervals and Triads

In this JGT lesson, jazz guitarist Leon Rodriguez explains intervals and triads in this music theory lesson specifically for guitarists.

What is a Triad? There are some that may argue that a triad is any 3 notes grouped together. Okay. Let them argue. Here and now, in this course, a triad is a group of three notes stacked in thirds.

Let’s talk about thirds. Every other note of the scale is identified as the interval of a third. However, the notes in a scale are not equidistant. A scale has two half steps in it, one per tetrachord. The distribution of those half steps dictates the Type of third from interval to interval. An interval is not the notes but the space between the notes, like a distance. A third will be either a Major 3rd (4 frets) or a minor 3rd (3 frets) within the set of intervals the major scale offers. That distribution of half steps gives us the reoccurring pattern: Major 3rd, minor 3rd, minor 3rd, Major 3rd because the 2nd and 3rd intervals contain a half step. If a 3rd above the root is 2-part harmony, we stack a 3rd above the 3rd for a triad.

Every language requires the basic need to spell therefore, it’s a ‘must learn.’ If you were inclined to learn to read notation, the first thing you learned or would learn are two mnemonics to help remember the names of the lines and spaces on the staff. Those same mnemonics will teach us the cycle of 3rds which is how we spell chords. Rhyming with ‘Line’ Is the sentence Every Good Boy Does Fine. Rhyming with ‘Space’ is the word FACE. Let’s put them together into a Cycle of 3rds, which is what they are. E G B D F A C E. We extrapolate mnemonics for triads from the cycle of 3rds; 7 triads, a 7-note cycle, 7 little mnemonics.

Step 1.) Get the 3- note name

Step 2.) ‘Dial’ in the key signature for accidentals by key.

Take a minute to notice the symmetry and order of both the key signature chart and our process of building chords. This is dependable methodology that can be trusted. Now let me add further to our admiration. Look at the column on the key signature chart labeled “Major Key”. It is the order that assigns sharps and flats to a given key. That is the all-important Cycle of 5ths. More on this later.

When we worked with 2-part harmony we began with a scale on the 2nd string so the 1st string was available to us to add the harmony notes. We had the roots on the 2nd string and the 3rds on the 1st

string. To build triads we need 3 notes built on each root note so we use our unison line to shift stringsets of the root-3rd string pair from the {21} stringset to the {32} stringset to reserve the 1st string for 5ths in our triads; our next 3rd interval in the building process. The 2nd string shifts 1 fret.

This is a clear example of how the unison line solves a problem of adding range exactly where we need it. In this case; higher notes to add the 5ths. Let’s mark this process. One shift up the unison line adds one string for higher notes and subtracts one string of lower notes in position! Add this important process to your guitaristic instincts for in-position range awareness. It’s an obvious-if-known fact.

Once we have opened up the 1st string, use the cycle of 3rds to add the 5ths: C major =C,E,G so think; Cows Eat Grass so the G is added to the first string, 3rd fret. Do Fine Always; add the A; 5th fret. etcetera.

In two-part harmony, the half steps gave us a Maj-min-min-Maj pattern. Now our 7th degree has been spelled as diminished triad; Root, min 3rd, flatted 5th since an F note is natural in the key of C major.