Students often ask me why they should use one sort of chord rather than another – say, a G7sus instead of a G7… or a C7(b9) as opposed to a C9. Music theory gives us a lot to say about the differences between chords. But there is an indispensable way of answering these questions that’s more direct, and people often overlook it.

You probably already have access to lots of great jazz recordings and lots of sheet music with chords — fake books and the like. If you don’t, your first step should be to fix that. ( Some advice about how. )

If you’ve got these things, all your answers about when and how to use chords are already at your fingertips. Here’s what I mean…

Perform Small Experiments

Suppose you’re wondering why Horace Silver used minor-major-7 chords in Nica’s Dream. The music for the song will show you that the first two chords of the melody (after the intro) are Bbm(Maj7) and Abm(Maj7). Listen to what they sound like on one of the classic recordings—Horace-Scope (1960) or the original Art Blakey and the Jazz Messengers (1956). Now imagine some similar chords he could have chosen instead and ask yourself why he didn’t use those. Why didn’t he use, for example, Bbm7 in place of Bbm(Maj7) and Abm7 instead of Abm(Maj7)? Well, what would it have sounded like? If you can imagine that, you’ll know exactly why he didn’t choose that option. Luckily, you don’t have to imagine it. Just play it that way yourself, and listen! (If you don’t play a chordal instrument, you can have a playalong app such as iRealPro or Band-in-a-Box play it for you.) Play the original version, then swap in the new chords for the original ones and play it again. It’ll sound something like this…

Here, first take a listen with the original chord changes to the first six bars of the melody – namely, Bbm(Ma7)→Abm(Ma7)→Bbm(Ma7):

And now modified to use minor 7 chords instead – namely, Bbm7→Abm7→Bbm7:

(Notice that one melody note is changed to accommodate the new chords.

Listen deeply. The modified version doesn’t sound terrible… but it doesn’t make for as compelling a song. What you are hearing is the answer, in its purest form, to the question, “Why didn’t Horace Silver use minor 7 chords at the beginning of the melody to Nica’s Dream”… and an answer, at least in part, to “Why did he use minor-major-7 chords?”

To answer that last question fully, you can pose other experiments too. What does it sound like to use major 7 chords there? Sus chords? Try them! Each offers a new perspective on the qualities of the minor-major-7 sound that makes it perfect for Nica’s Dream. (Not to mention an unusual vantage on all the other chords that are less appropriate!)

For an even fuller picture, choose a song that doesn’t use minor-major-7 and change it so that it does. Staying with Horace Silver, you could take Silver’s Serenade, whose first eight bars are entirely minor 7 chords. Change them to minor-major-7 and you’ll hear an example where the same qualities of the minor-major-7 sound that made it great for Nica’s Dream no longer serve the cause at hand.

Get Creative With Your Questions

In other words, the great songs tell you everything you need to know about the chords they use. You have all the answers; you just have to come up with the questions. Why didn’t Gershwin use an A9 instead of an A7b9 in this spot? What made Freddie Hubbard use an altered chord here? What made Harold Arlen insert a diminished chord?

These and hundreds others like them are crucial questions, and to learn the answer to any one all you have to do is a little experiment.

Another Example

The method doesn’t just apply to single chords. Suppose you want to learn more about a particular harmonic device—say, the backdoor ii-V. Recall that a backdoor progression is an alternative to a standard ii-V-I, in which the dominant chord resolves to the destination not by descending a fifth but by ascending a whole step. If you’re looking to understand its use, find an example by a great composer and ask yourself why he/she used a backdoor instead of a standard ii-V-I. And answer this question by playing the song first as written, then with a standard ii-V-I substituted for the backdoor.

For instance, look at the beginning of Tadd Dameron’s Lady Bird. The chord changes of the first five bars are:

which sounds like this:

When we substitute a standard ii-V-I progression for the backdoor progression in bars 3-5, the changes become:

which sounds like this:

Once again, I’ve altered the melody to accommodate the chord changes, while otherwise trying to keep it within the general style of the song.

It’s not that the result sounds bad. Rather, it sounds different in a way that doesn’t serve the song as well as the original did.

Use Your Words

In each case, how would you describe the difference made by the new chords? Try to put it into words. Be poetic if normal adjectives don’t do the trick. Use imagery. Is one colder? Brighter? More like a smoke-filled room? A drive on the open road? Comfort food? Even if you can’t quite capture the sound differences using words, the effort will help you get a better feel for them and help the memory last.

More Examples

• Altered chords
  • Recorda Me (Joe Henderson) — replace the E7alt at the end of the melody with a variety of other dominant chords such as E13, E9(#11), E13b9, even E9sus. The melody note is G♮, the sharp 9, so you will have to change it for some of the chords.
• Sus chords
  • Maiden Voyage (Herbie Hancock) — replace D7sus and F7sus with D7 and F7.
  • Some Other Time (Leonard Bernstein) — replace the sus chords in the first three bars of the melody (G7sus) with G7.
• Lydian
  • Happy Birthday — If we play it in the key of F, the chord of the third to last measure is Bb major. Replace the melody note there (E) with Eb. Whereas the original E gave the Bb chord a Lydian sound—implicitly a BbMaj7(#11)—the Eb gives it a simple major (Ionian) sound. Note that the Lydian E (the raised fourth of the Bb chord) sounds particularly appropriate here because the Bb is the four chord of F. As a result, the E is diatonic to F major, the key of the song. Compare this to an example where the Lydian note is not diatonic to the song’s key:
  • Blue in Green (Miles Davis / Bill Evans) — change the BbMaj7(#11) of the first and fifth bars to a BbMaj7, and raise the melody note from E to F. (Unlike Happy Birthday, lowering the melody to Eb is not an option here. That’s because the note lasts 3 beats, and Eb is the fourth note of a major scale, which is too dissonant to be held that long. By contrast, the tension-filled Eb note in the modified Happy Birthday lasts only a beat before resolving downward.)
• Minor ii-V progressions
  • I Love You (Cole Porter) — replace the first two chords of the melody (Gm7b5→C7b9) with Gm7→C9.
  • Blue Bossa (Kenny Dorham) — replace bars 5-6 and bars 13-14 (Dm7b5→G7alt) with Dm7→G9.

Healthy Curiosity

If there’s a broad lesson to be drawn, it’s this: engineers who want to know how a gadget works often take it apart to look inside. You may have done that with your toys as a kid. Don’t be afraid to do it with a great song! Get under the hood of the song and make changes and see what happens. Put yourself in the shoes of the composer trying to write the song and imagine what options they had and why they made the choices they did. We can look at the great songs as beautiful feats, not only of creativity, but of engineering. And luckily, after we pick them apart and swap out lots of their parts, they’re much easier to put back together than a favorite toy.