How to remember base triads

There are four basic triads in Western music: major, minor, diminished, and augmented. Times twelve possible roots, that's 48 chords. You don't need to memorise 48 chords. You need to memorise four interval patterns and apply them to any root.

This article walks through the four shapes, the rule that makes them stick, and a couple of memory tricks for when the spelling gets weird.

The rule: stack two thirds

Every basic triad is built by stacking two thirds on top of a root. The only thing that changes between the four chord types is whether each third is major (4 semitones, e.g. C → E) or minor (3 semitones, e.g. C → E♭).

• Major triad: major third, then minor third. (C → E → G.)
• Minor triad: minor third, then major third. (C → E♭ → G.)
• Diminished triad: minor third, then minor third. (C → E♭ → G♭.)
• Augmented triad: major third, then major third. (C → E → G#.)

That's the whole system. If you can name the third above any note (and you can, with practice — drilling intervals is the fastest way), you can build any of the four triads on any root.

A memory trick: the symmetric pair and the asymmetric pair

Two of the four triads are symmetric (both thirds the same):

• Diminished = two minor thirds.
• Augmented = two major thirds.

Two are asymmetric (different thirds):

• Major = major-then-minor (the "happy" one starts with the bigger interval).
• Minor = minor-then-major (the "sad" one starts with the smaller interval).

If you can remember "major starts big, minor starts small," and "diminished is all small, augmented is all big," you have the four triads encoded as a tiny rule rather than a list.

The spelling rule that catches everyone

When you build a triad, every note must use a different letter name, advancing two letters at a time: 1, 3, 5. C major is C–E–G. F# minor is F#–A–C#. E♭ diminished is E♭–G♭–B♭♭ (yes, double-flat — that's correct).

The double-sharps and double-flats look intimidating, but they show up specifically because the stack-of-thirds rule must be honoured. Once you accept that, the spelling becomes mechanical.

Drill it, don't memorise it

Looking up "what are the notes in B♭ diminished?" once and forgetting it next week is rote memorisation, and it doesn't scale. The faster path is to drill the rule with flash cards: see a chord name, build it from scratch, check yourself. Repeat until it's automatic.

The Chord Trainer on this site does exactly this — it shows you a chord name (C aug, F# dim, B♭m, etc.) and asks you to spell out the three notes. It runs through every quality you've toggled on, with a timer to track your improvement.

Beyond the four basics

Once the four basic triads are reflexive, the same logic extends to seventh chords (add another third on top), ninth chords (add another), thirteenth chords (one more). The interval-stack rule never changes — you're just chaining more thirds on top of the same root.