Ninths and thirteenths

A dominant seventh has four notes. Put the ninth on top and you have five; put the thirteenth above that and you have the sound of a horn section. Nothing about the harmony has changed — it is still the I, the IV or the V — but the chord is thicker and it moves differently under a singer.

The first is the open E9 taken up the neck, and its ninth is the top note, under your little finger. The second has its root on the fifth string. It is the B♭9 from the first fret moved up to the fifth, and it is the D9 most players reach for first. Its ninth sits on the second string, under the small barre. In both shapes the ninth is the note that changes the color, so listen for it.

A thirteenth chord has more notes than a guitar has fingers, so nobody plays all of them. What makes it that chord is the third, the seventh and the thirteenth; the fifth goes first and the ninth goes next, which is why the shapes above look thinner than the name suggests.

Sliding in from a fret below

These chords are almost never struck cold. Play the shape one fret below where it belongs, strike it, and slide it up on the beat — the whole chord arrives from underneath, which is the sound of jump blues and of the players who came out of it.

It works because every note moves by the same step. Slide from a fret below and each voice arrives a semitone late, which is the same leaning motion you have been playing one note at a time since Part 3, played by five notes at once.