If the triad trainer at the end of the last lesson felt hard, that's normal. The concept of triads is simple, but actually recognizing them on the fly takes work. This lesson is about making that easier.

You know the musical alphabet forward and backward because it's literally the same alphabet that you learned from Sesame Street when you were 4 years old. C D E F G A B, no problem. But chords aren't built in steps. They're built in thirds. And if you want to build chords quickly, you need to be able to skip through the alphabet in thirds and fifths as fluently as you can recite it in order.

This is pure memorization. There's no trick to it, no shortcut. You just have to drill it until it's automatic. Luckily for you, it really isn't that hard, and spending the time to do this now will pay off for as long as you play music.

A third means you skip one letter name. Starting on A:

A — C — E — G — B — D — F — A

Every other letter. The pattern works from any starting note:

D — F — A — C — E — G — B — D

G — B — D — F — A — C — E — G

It's always the same seven letters cycling around. This is how triads work. Pick any starting note, grab the next two notes in the thirds sequence, and you have a triad. A-C-E. D-F-A. G-B-D. Once you can fly through these without hesitating, building chords becomes nearly instant.

Not all thirds are the same size. You covered this in the intervals lesson, but here's the quick version:

• A major third = 4 half steps
• A minor third = 3 half steps

Among the natural notes (no sharps or flats), there are only two sizes and only seven pairs:

Major thirds (4 half steps): C-E, F-A, G-B

Minor thirds (3 half steps): D-F, E-G, A-C, B-D

Three major, four minor. If you can recall which are which without counting half steps, you can identify any natural triad quality instantly. A major triad has a major third on the bottom. A minor triad has a minor third on the bottom. Know your thirds, know your chords.

Once you know the natural thirds, sharps and flats are easy. An accidental shifts one note by a half step, which shifts the interval size by a half step. You don't need to memorize a bunch of rules. Just use the natural version as your reference point.

What kind of third is F#-A? Well, you know F-A is a major third. Raising the bottom note shrinks the interval by a half step. So F#-A is a minor third.

Eb-G? E-G is a minor third. Lowering the bottom note stretches the interval by a half step. Eb-G is a major third.

Ab-C? A-C is a minor third. Flatting the bottom stretches it. Ab-C is a major third.

If BOTH notes have accidentals? That just shifts the whole interval, so it’s quality is the same as the natural one B-D is a minor third, so Bb-Db is a minor third.

This is why memorizing the seven natural pairs matters — they become your instant reference for every combination you'll run into.

Fifths skip three letter names. Starting on E:

E — B — F — C — G — D — A — E

Going the other direction (fourths):

A — D — G — C — F — B — E — A

Fifths matter for chords because the outer two notes of a triad are always a fifth apart. D-F-A: D to A is a fifth. E-G-B: E to B is a fifth.

You already learned that the circle of fifths is a cheat-code for knowing how many sharps or flats are in a key… so committing this to memory now unlocks the ability to remember every key signature with one simple pattern and a couple of rules.

Here’s another one: The order of sharps and flats as they appear in key signatures is ALSO this pattern. (sharps start on F and go in fifths, flats start with B and go backwards, in fourths)

Almost every natural fifth is a perfect fifth (7 half steps). There's one exception:

B to F is a diminished fifth (6 half steps — a tritone).

Every other natural-note fifth (C-G, D-A, E-B, F-C, G-D, A-E) is perfect. That one odd pair is why B builds a diminished triad instead of a major or minor one, and why the circle of fifths goes to F# at the bottom, after B.

Here's another freebie. You can now find relative major and minor keys instantly, because relative keys are a third apart.

The relative minor of any major key starts on the 6th degree, which is the same as dropping down one third. Go backwards one step in your thirds sequence and you're there.

G major? Drop a third: E minor.

Bb major? Drop a third: G minor.

Eb major? Drop a third: C minor.

Going the other way — relative major from a minor key — just go up one third.

F# minor? Up a third: A major.

D minor? Up a third: F major.

No counting to the 6th degree, no looking anything up. If you know your thirds, you know every relative key pair.

This is the kind of thing that gets better with five minutes a day, not an hour once a week.

Thirds drill: Pick a random starting note. Say the letters in thirds as fast as you can until you're back where you started. F-A-C-E-G-B-D-F. Then pick another note. Do it until you don't have to think.

Fifths drill: Same thing, but in fifths. D-A-E-B-F-C-G-D. Then start on Bb. Then start on F#. Go until it's automatic.

Quality drill: Pick random pairs of natural notes a third apart. Is D-F major or minor? How about G-B? A-C? Don't count half steps, recall from memory. Then throw in accidentals: what about D-F#? Eb-G? Get it wrong, note which ones trip you up.

On your instrument, play the thirds sequence up and down while saying the note names out loud. Hearing the intervals while naming them helps lock it in. The Thirds and Fifths reference sheet has all the tables in one place if you want something to quiz yourself against.

Start with the natural notes. Major or minor? Don't count half steps if you can avoid it.

Once those feel automatic, turn on accidentals. Use the natural pair as your reference point.

Now try the relative keys. Given a key, name its relative major or minor. Just go up or down one third.

Beyond the trainers, spend five minutes a day reciting thirds and fifths sequences out loud from random starting notes. On your instrument, play the thirds sequence up and down while saying the note names. It clicks faster than you'd think.

The Interval Trainer is also great here. Set it to 3rds and 5ths only and drill until they're instant. And if you just want the tables without the explanations, grab the Thirds and Fifths reference sheet.