OK, so far we have learned a LOT about how chords are constructed. Everything we've learned so far has been chords built by stacking thirds, but it is possible to build chords with other intervals too.

The chords that we're building here are technically derived from the related third-stacked chords, but either add to, or move notes around to get a different flavor.

Every chord we've built so far has had a third. That third is the note that tells you whether a chord is major or minor. It's the single most important note in determining a chord's character.

So what happens when you take it out?

You get a suspended chord, or "sus" chord. Instead of a third, you've got either a 2nd or a 4th. No third means the chord is neither major nor minor.

If you play guitar, you've almost certainly played sus chords before. That Dsus4 you learned early on? That's this. And if you play piano, you've probably stumbled into them just by moving one finger. All you're doing is taking the third and nudging it up or down by a step.

Start with any triad, major or minor, and move the third up to the next note in the key. That note is the perfect fourth above the root, and now you've got a sus4 chord.

Take a C major triad: C — E — G. Move the E up one scale step to F, and you get Csus4: C — F — G.

The root and fifth stayed put. Only the third moved. That one note completely transforms the chord's character.

Same thing starting from G major: G — B — D. Move the B up one scale step to C: Gsus4 is G — C — D.

Sus4 chords have a feeling of anticipation, like they want to fall back down to the major chord. Play a Gsus4 and then a G major, one after the other. Hear how the sus4 "resolves" when the 4th drops back down to the 3rd? That tension-and-release move is one of the most common uses of sus chords in pop and rock.

Another way to think about it: a sus4 is just root, 4th, 5th. But framing it as an alteration of a chord you already know is more useful in practice.

In chord charts you'll see these written as Csus4, Gsus4, Dsus4, etc. Sometimes just Csus with no number, which almost always means sus4.

Same idea, opposite direction. Take the third and lower it one scale step. Now it's a major second above the root, and you've got a sus2 chord.

C major is C — E — G. Drop the E down one step to D: Csus2 is C — D — G.

D major is D — F# — A. Drop the F# down one step to E: Dsus2 is D — E — A.

Sus2 chords feel open and airy. They don't have that same "pulling toward resolution" feeling that sus4 chords do. They're more content to just sit there. You'll hear them a lot in acoustic pop, folk, and post-rock where that open, ambiguous sound works well.

Written as Csus2, Dsus2, etc.

Here's the thing about sus chords that makes them special: without the third, there's nothing telling your ear "this is happy" or "this is sad." The chord is genuinely neutral. That makes them incredibly useful when you want a chord that adds movement or color without committing to a mood.

Songwriters use this constantly. Think of the opening of "Crazy Little Thing Called Love" (Dsus4 to D), or the iconic riff in "Pinball Wizard" (sus4 chords everywhere). The Who basically built a career on sus chords.

Sus chords replace the third. Add chords keep it and add another note on top.

An add9 chord is a triad plus the 9th. The 9th is the same note as the 2nd, just up an octave. So Cadd9 is C — E — G — D:

The crucial difference: the third (E) is still there. This is NOT the same as sus2. A Csus2 is C — D — G (no third). A Cadd9 is C — E — G — D (third is present, 9th is added on top).

Gadd9: G — B — D — A

Add9 chords are lush and full. They're one of the most popular "make this chord sound a little more interesting" moves in pop and folk music. If you play guitar, you might know the famous open Cadd9 shape (which is probably the most played add chord in history).

You might also see add11 chords, which add the 11th (same as the 4th, up an octave) while keeping the third. These are less common, but they exist.

This is a common mix-up. A Cadd9 is a triad with an added 9th: C — E — G — D. Four notes, no seventh.

A C9 (a "ninth chord") is a dominant seventh chord with a 9th stacked on top: C — E — G — Bb — D. Five notes, includes the seventh. That's an extended chord, and we'll cover those in a later lesson.

The "add" tells you it's just the triad plus that one extra note, nothing in between.

Chord	Notes	What changed
C major	C — E — G	Normal triad
Csus4	C — F — G	3rd raised one scale step
Csus2	C — D — G	3rd lowered one scale step
Cadd9	C — E — G — D	3rd stays, 9th added on top

• Synthet — the sus chord — You're familiar with this guy's upbeat videos. Short and fun, and he does a great job explaining why sus chords work the way they do.

• Charles Cornell - These Chords Are SUS... - just what it says on the tin, a little more techincal than Synthet's bouncy fun video.

• 8-bit Music Theory — 5 Sus Chords to Get Yourself a Girlfriend — Not only a good explainer, it has some fun examples from video game and film music that show how sus chords are used in context.

Play a major chord you're comfortable with, then move the third up one half step to make it sus4. Play back and forth between the two. Then try moving the third down a whole step to make it sus2. Get used to how each one feels compared to the plain major chord.

Try this on a few different roots. The shapes will be different, but the relationships are always the same: the third either moves up to a 4th, drops down to a 2nd, or stays put while you add a 9th on top.