TRIAD

The intervals of a third and a fifth, added to the root, form a special three-note chord called a triad. These two intervals help reinforce the root, producing a clear and intelligible sound.

MAJOR TRIAD

The major triad has a bright and clear sound, and the method to build it is simple: start from any note, which we call the root, and add the ascending intervals of a third and a fifth. In terms of semitones, the third is 4 semitones above the root, and the fifth is 7 semitones above the root. Once we have identified the root, third, and fifth, our triadic chord is ready and can be played harmonically or melodically.

EXAMPLE: C MAJOR TRIAD

	semitones	notas	ratio
ROOT	-	C	1/1
THIRD	+4	E	5/4
FIFTH	+7	G	3/2

EXAMPLE: F MAJOR TRIAD

	semitones	notas	ratio
ROOT	-	F	1/1
THIRD	+4	A	5/4
FIFTH	+7	C	3/2

MINOR TRIAD

The minor triad is another very important triad, more melancholic and introspective compared to the major triad. Of course, its character also depends on the tonal context in which it is placed. The method to build it is similar to the one already seen for the major triad; the only difference is that the third interval is 3 semitones above the root, instead of 4. With a root note, its minor third, and its fifth, you can play a minor triad, either harmonically or melodically.

EXAMPLE: C MINOR TRIAD

	semitones	notas	ratio
ROOT	-	C	1/1
THIRD	+3	Eb	6/5
FIFTH	+7	G	3/2

EXAMPLE: F MINOR TRIAD

	semitones	notas	ratio
ROOT	-	F	1/1
THIRD	+3	Ab	6/5
FIFTH	+7	C	3/2

STACKING OF THIRDS

Another method to obtain a major triad is to start from the root, find the major third, and then add a minor third above the major third to reach the fifth. The 4 semitones of the major third combined with the 3 semitones of the minor third give exactly the 7 semitones needed to reach the fifth.

	C MAGGIORE	GMAGGIORE	D MAGGIORE
Fondamentale	C	G	D
+3a maggiore (4 semitoni)	E	B	F#
+3a minore (3 semitoni)	G	D	A

In the same way, we can form a minor triad by identifying the minor third above the root (3 semitones) and adding a major third (4 semitones) on top of it to reach the fifth.

	C MINORE	G MINORE	D MINORE
Fondamentale	C	G	D
+3a minore (3 semitoni)	Eb	Bb	F
+3a maggiore (4 semitoni)	G	D	A

THE PHYSICAL ASPECT OF THE MAJOR TRIAD

If we relate the frequencies of the root to those of each interval in a major scale, we notice that only two intervals provide a ratio that is a power of 2 and less than or equal to four: the fifth interval (3/2) and the third interval (5/4). When the denominator is a power of 2, the period of the resulting wave refers back to the root, reinforcing and confirming it. If the denominator is low, that is, less than four, the resulting wave will have a short period, and its periodicity will be perceived more clearly. This explains, from a psychoacoustic perspective, why the major triad is such an intelligible chord.

CONCLUSION

Memorizing the third and fifth of each root is certainly an essential milestone for a professional musician, not only because of the cultural importance of these intervals but also due to their immutable psychoacoustic characteristics. Knowing the third and fifth of every note by heart gives you the triad already in your hands. However, there is no need for excessive memorization: without demanding too much from oneself, through experience and conscious playing, one gradually becomes familiar with these intervals over time.