Triads: three notes, one mood

Play three notes together in the right spacing and something new happens: your ear stops hearing three notes and starts hearing one object with a mood. That object is a chord, and the smallest, most important kind is the triad: a root, a third, and a fifth, stacked. Almost every chord you have ever heard is a triad or a triad wearing accessories.

Build one

The slider picks the root note; the buttons pick the shape (the numbers are semitone offsets, exactly the rows you would count on the piano roll). The name in the readout is not hardcoded: it comes from the same chord recognizer that reads Ableton Live sets in the Theory Aide extension, listening to the actual notes you built:

Start with Just the fifth and really listen: it is solid but blank, a frame with no picture. Now press Major. One added note and suddenly the sound has a mood. Switch to Minor while it plays and feel the single semitone drop change everything.

Two thirds, stacked

A triad is two intervals from the last article stacked on top of each other. The bottom note is the root: the note the chord is built from and named after. Seven semitones up sits the fifth, the sturdy 3:2 frame. And in between sits the third, the note that decides the mood: four semitones up (a major third) and the chord is bright; three semitones up (a minor third) and it shades over. On the piano roll a triad is just three rows: root, root plus 3 or 4, root plus 7. That one-row difference in the middle is the entire distance between happy and sad, which may be the highest ratio of meaning to semitones anywhere in music.

The four flavors

Move the third and the fifth around and there are exactly four triads:

• Major (0·4·7): bright, settled, home. The major third from the interval demo, now with a frame around it.
• Minor (0·3·7): the same frame, the third lowered one row. Shaded, serious, not "sad" so much as deeper in the picture.
• Diminished (0·3·6): the fifth shrinks too, and the frame itself goes unstable. A diminished chord leans hard toward somewhere else; it is tension wearing a chord costume.
• Augmented (0·4·8): the fifth stretches instead. Dreamlike, symmetric, unresolved; the rarest of the four in the wild, and instantly recognizable once you've tasted it.

Major and minor carry nearly all popular music between them; diminished and augmented are the spices you reach for on purpose.

In your music

Draw any three-note stack into a Live clip and you have done everything this article describes; the piano roll makes triads visible as their row pattern. When the Theory Aide extension explains a clip or spells your arrangement's harmony beat by beat, the code doing the naming is the exact code in the demo above, unmodified: it measures the intervals in the stack and recognizes the flavor. Which triads a key gives you for free, and why they come out major in some slots and minor in others, is the next article on the harmony trail, and it is where chords stop being objects and start being a language.