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Have you ever played with a vocalist that asked you to play tunes in different keys? Do you want to learn how to transpose jazz chords for your piano playing? With the number method, you will learn the easiest way to transpose chord progressions into any key in 2 steps:

1. Learn diatonic 7th chords using Roman numerals
2. Analyze chord progression using Roman numerals

Let’s dig in!

Step 1: Diatonic 7th Chords Using Roman Numerals

One of Jonny’s favorite things about this method is that once you learn the chord quality and Roman numeral of each chord, it stays the same for all 12 keys! Thinking about chords in terms of numbers makes transposing and memorizing tunes a lot easier, and a lot more fun!

One of the keys to using this method is being aware of the chord quality of each of the seven 7th chords in a Major key:

We call these diatonic chords because each of these seven chords come from the same key. You’ll notice that we are building 7th chords starting on each note of the scale, and retaining the key signature as we move through them. The I chord is always a Major 7 chord, the ii chord is always a minor 7 chord, the iii is minor 7, the IV is Major 7, V is dominant 7, vi is minor 7, and vii is half-diminished (or minor 7 b5). This is the case for all 12 keys: no matter what key you’re playing in, these chord quality rules are the same. Major chords are identified with uppercase numerals and minor chords with lowercase numerals.

Familiarity with all 12 Major scales will pay huge dividends when it comes to transposing. The better you know the scale degree of each note of each scale, the easier this method is to use. Practice quizzing yourself on all seven scale degrees of each scale. For example, ask yourself “What’s the 6th of C? What’s the 2nd of F#? The 4th of G?” The faster you can recall the scale degree, the better!

Memorize the chord quality of each scale degree. This is key to transposing successfully! Next, let’s move on to applying this with harmonic analysis.

Step 2: Transpose Jazz Chords by Analyzing Chord Progressions with Roman Numerals

Now for the fun part! Let’s look at the chord progression for Jonny’s original tune:

Don’t forget that you can follow along with this chord progression using our Smartsheet! Right away, you can see that some of these chords don’t line up with what they should be from our diatonic 7th chord chart above. D7 is the VI chord, but it should be minor 7, not dominant 7! What gives? This is an example of a concept in music theory called secondary dominants.

SECONDARY DOMINANTS

As you can see from our diatonic 7th chords, only the V chord is a dominant 7th chord. This is a key concept to understanding harmony: the V chord always leads the ear to the I chord. The V chord can resolve either to Major I or minor i. Try playing C7, then F Major: then C7 to f minor. You’ll see how C7 leads the ear to both F Major and f minor. Cool!

The V chord in any key is the primary dominant chord. Secondary dominant chords are borrowed from other keys and used within the original key. For example, the second chord in Jonny’s tune is D7. While D is the 6th of F (and a 7th chord built on D should be the vi-7 chord), D7 does not belong in the key of F. The 3rd of this chord is F#, which definitely clashes with F! D7 is a clear secondary dominant.

By working backwards, it’s easy to figure out where a secondary dominant chord should lead. Since we know a dominant 7 chord must be the V chord of any key, and we know D is the fifth of G (see why you should know your scale degrees really well?), then the next chord should be either GMaj7 or Gmin7. As you can see, the next chord is Gmin7! This V-I motion leads the ear to “accept” the secondary dominant chord because it resolves correctly to Gmin7, and it also adds some nice musical color and harmonic motion within the chord progression. Awesome! Let’s continue by looking at the rest of the chord progression.

MOVING ON

Look at the root of each chord in the progression and identify the scale degree of the root in relation to the scale. C7 follows Gmin7, which is the V chord. That measure repeats, (iimin7  V7), then we have a I6 chord. In jazz, pianists and composers take certain liberties with chord quality depending on the color they want. In this instance, F6 is a substitute for FMaj7. They are both Major chords, but F6 has a bit of a different musical color.

The next chord is Bb7, which is the IV chord. However, this chord is a dominant 7 chord rather than a Maj7 chord, indicating a secondary dominant! Since this secondary dominant chord is Bb7, we expect the next chord to be EbMaj7 or Ebmin7. But it’s Amin7! In this case, Bb7 is a tritone substitution of E7, which is the V of iii (Amin7). Without going into too much detail, dominant 7 chords can be substituted with another dominant chord a tritone away because both chords function the same way.

The next measure begins with the iii chord, then is followed by biii diminished (Abdim7). In a chord progression like this, we expect to see chords move by 4th, so this chord “should” be Dmin7 or D7. This is another example of a tritone substitution, and using a diminished chord here hearkens back to jazz from the 1920s and 1930s. After Abdim7, we see a fairly straightforward progression of iimin7, V7 of ii, iimin7, V7. The last measure consists of a common turnaround in jazz: iii, VI, ii, V.

You can see that the number method is the easiest way to transpose jazz chords since the Roman numerals and chord qualities are the same across all 12 keys. Try applying the number method to play this chord progression in a few different keys. Jonny likes practicing with unrelated keys to really solidify the concept. He recommends keys a Major or minor 3rd apart, for example play this chord progression in F, D, B, and Ab. Once you can do it in a few keys, it’s easy to transpose jazz chords on piano in any key!

If you want to learn more about the theory behind this method, check out our Passing Chords & Reharmonization 1 and Passing Chords & Reharmonization 2 courses.

You can dig in to a lot more detail in transposing with our Transposing a Lead Sheet 1 and Transposing a Lead Sheet 2 courses.

Thanks for learning, and see you in the next Quick Tip.

Blog written by Austin Byrd / Quick Tip by Jonny May

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