Module 11: Harmony II: substitution and reharmonisationLesson 6advanced⏱ 2 hours + three weeks of daily practice

Reharmonising a melody

Put the whole module to work: a method for choosing new chords under a given melody, an original eight-bar melody reharmonised three different ways with every substitution explained, and guidelines for doing it to the tunes you play.

Why reharmonise

A standard has a melody and a set of chords, and the chords were chosen once, by one person, for one arrangement. Everybody who has played the tune since has changed them: a pianist adds a backdoor cadence, a guitarist slips in a tritone sub, an arranger rewrites the last four bars with a chromatic bass line. Reharmonisation is the craft of choosing different chords under the same melody, and it is the point at which the five devices of this module stop being theory and become choices you make in real time. This lesson gives you a method, then applies it to an original melody three times, in three different styles, so that you can see every decision and the reason for it.

The method

Reharmonisation has one hard constraint and a lot of freedom. The constraint: every melody note must make sense against the chord under it, as a chord tone or as an available tension. The freedom: subject to that, any chord that leads convincingly to the next one is allowed. In practice you work in this order.

1. Analyse the original. Write the Roman numerals, find the cadences, and mark which melody note falls on each chord change. This tells you what the melody needs from the harmony.
2. Decide what you want. A darker ending? A walking chromatic bass? A modern, floating sound? Each goal points at different devices.
3. Pick a device for each spot from the six below, and test the melody note against the new chord. If the note is the root, 3rd, 5th, 7th, 9th, 11th (on minor chords), #11 (on dominant and major chords) or 13th of the new chord, it works. If it is a half step above a chord tone, it usually does not.
4. Check the bass line on its own. A good reharmonisation has a bass line you could sing.
5. Play it and listen. Theory decides what is possible; your ear decides what stays.

The six devices, each from one of the earlier lessons:

• Substitution by function. Replace a chord with another of the same function: I with iii or vi, IV with ii, V with viiø7 or with a dominant on a different root (Modules 2–3).
• Secondary dominants and related iis in front of any diatonic target (lesson 1).
• Tritone substitution of any dominant, which also gives you chromatic bass motion (lesson 2).
• Diminished passing chords between chords a whole step apart, and rootless 7b9 shapes (lesson 3).
• Modal interchange: iv, bVImaj7, bVII7, iiø7, bIImaj7 and the backdoor (lesson 4).
• Constant structure and chromatic mediants: one chord quality moved in parallel, or maj7 chords a major 3rd apart (lesson 5).

A chromatic bass line is not a device of its own but a goal that several devices serve: a passing diminished chord, a tritone sub and a rootless 7b9 all give you a half-step bass move, and a good reharmonisation often chains them.

The melody

Here is an original eight-bar melody in C, the kind of simple diatonic line that thousands of standards are built on. The chords are the plain diatonic harmony it was written over: I | ii V | vi | ii V | I | IV | ii V | I. Learn it until you can sing it, because you will be judging every reharmonisation by whether this line still sounds right on top.

\tempo 96
.
\ts 4 4
:4 9.3{ch "Cmaj7"} 8.2 :2 7.1 | :4 5.1{ch "Dm7"} 6.2 :2 3.2{ch "G7"} | :2 3.1{ch "Am7"} :4 5.2 5.3 | :4 3.2{ch "Dm7"} 6.2 :2 3.1{ch "G7"} | :4 9.3{ch "Cmaj7"} 8.2 :2 8.1 | :2 10.2{ch "Fmaj7"} :4 8.2 6.2 | :4 3.2{ch "Dm7"} 5.3 :2 3.2{ch "G7"} | :1 1.2{ch "Cmaj7"} |

Before reading on, do step 1 of the method yourself: for each bar write the melody note that falls on each chord and its degree in that chord. You should find that the melody sits almost entirely on roots, 3rds and 5ths, which is what makes it easy to reharmonise: a note that is the 5th of one chord is the 3rd of another and the 7th of a third.

Reharmonisation A: secondary dominants and related iis

The first version keeps the diatonic skeleton and adds motion: a secondary dominant in front of every important diatonic target, so that the bass moves in 5ths and every bar has a chord change. The chords are | Cmaj7 A9 | Dm7 G7 | Em7 A7#9 | Dm7 G7 | Cmaj7 C7 | Fmaj7 | D9 G7 | Cmaj7 |. In the notation the melody is the upper voice and the chords are the lower voice, played as three-note shells (root, 3rd, 7th) struck on beats 1 and 3 and allowed to ring under the melody. The melody is fingered to sit within a four-fret span of each chord, which sometimes means playing the same pitch on a different string than in the plain version.

\tempo 96
.
\ts 4 4
\voice :4 9.3 8.2 :2 7.1 | :4 5.1 6.2 :2 3.2 | :2 3.1 :4 5.2 5.3 | :4 3.2 6.2 :2 3.1 | :4 9.3 8.2 :2 8.1 | :2 10.2 :4 8.2 6.2 | :4 3.2 5.3 :2 3.2 | :1 1.2 |
\voice :4 (8.6 7.5 9.4){ch "Cmaj7"} r (5.6 5.4 6.3){ch "A9"} r | (5.5 3.4 5.3){ch "Dm7"} r (3.6 2.5 3.4){ch "G7"} r | (0.6 0.4 0.3){ch "Em7"} r (5.6 4.5 5.4){ch "A7#9"} r | (5.5 3.4 5.3){ch "Dm7"} r (3.6 2.5 3.4){ch "G7"} r | (8.6 7.5 9.4){ch "Cmaj7"} r (8.6 8.4 9.3){ch "C7"} r | (8.5 7.4 9.3){ch "Fmaj7"} r (8.5 7.4 9.3) r | (5.5 4.4 5.3){ch "D9"} r (3.6 2.5 3.4){ch "G7"} r | :1 (3.5 2.4 4.3){ch "Cmaj7"} |

Bar by bar:

• Bar 1, A9 (V7/ii). The second half of the bar gets the dominant of the Dm7 that follows. The melody note B is the 9th of A, so the chart says A9 rather than A7; the shell you play is just A7 and the melody supplies the 9th. Nothing has to change in your fingers for the chord to be an A9.
• Bar 3, Em7 and A7#9 (iii and V7/ii). The vi chord is replaced by iii, a substitution by function (both are tonic-family chords and both contain the melody's G and E), and the second half of the bar becomes V7/ii again. The melody's C over A7 is its #9, the blues note of the dominant, so the symbol is A7#9. Had the melody been a C#, this would have been a plain A7; had it been a D, you would avoid the chord.
• Bar 5, C7 (V7/IV). The tonic turns into the dominant of the IV chord in bar 6. The melody note C is the root of C7, the safest note there is.
• Bar 7, D9 (V7/V). The ii chord becomes II7, a dominant pointing at G7. The melody D is its root, the C on beat 2 is its 7th, and the D at the end of the bar is the 5th of G7 as before. IVmaj7 to II7 is one of the oldest moves in the songbook.

The result is a melody that has not changed a note sitting on a bass line that moves C–A–D–G–E–A–D–G–C–C–F–D–G–C: almost entirely 5ths. That is the sound of a 1930s standard.

Reharmonisation B: chromatic bass, tritone subs and diminished chords

The second version wants a bass line that moves by half steps. The chords are | Cmaj7 C#m7b5 | Dm7 G7 | Em7 Ebdim7 | Dm7 Db7#11 | Cmaj7 Gb7#11 | Fmaj7 Eb9 | Dm7 Db7b9 | Cmaj7 |. Three different devices supply the half steps, and bar 2 is left alone on purpose: a reharmonisation does not have to change every bar, and the untouched ii–V is what makes the chromatic bars sound like choices.

\tempo 96
.
\ts 4 4
\voice :4 9.3 8.2 :2 7.1 | :4 5.1 6.2 :2 3.2 | :2 3.1 :4 5.2 5.3 | :4 3.2 6.2 :2 3.1 | :4 9.3 8.2 :2 8.1 | :2 10.2 :4 8.2 6.2 | :4 3.2 5.3 :2 3.2 | :1 1.2 |
\voice :4 (8.6 7.5 9.4){ch "Cmaj7"} r (9.6 9.4 9.3){ch "C#m7b5"} r | (5.5 3.4 5.3){ch "Dm7"} r (3.6 2.5 3.4){ch "G7"} r | :2 (0.6 0.4 0.3){ch "Em7"} :4 r (6.5 7.4 5.3){ch "Ebdim7"} | (5.5 3.4 5.3){ch "Dm7"} r (4.5 3.4 4.3){ch "Db7#11"} r | (8.6 7.5 9.4){ch "Cmaj7"} r (9.5 8.4 9.3){ch "Gb7#11"} r | (8.5 7.4 9.3){ch "Fmaj7"} r (6.5 5.4 6.3){ch "Eb9"} r | (5.5 3.4 5.3){ch "Dm7"} r (4.5 3.4 4.3){ch "Db7b9"} r | :1 (3.5 2.4 4.3){ch "Cmaj7"} |

• Bar 1, C#m7b5. The passing chord between C and D. Look at the table: C#m7b5 is A9 without its root, so this is the V7/ii of version A with its bass moved up to the 3rd, the same trick as the passing diminished chord in lesson 3 but with a half-diminished colour because the melody's B (the 7th of C#m7b5) would clash with the Bb of a C#dim7. The bass goes C–C#–D.
• Bar 3, Em7 and Ebdim7. The vi becomes iii again, and the descending passing diminished chord from lesson 3 takes the bass from E to Eb to the D of bar 4. The melody's C is the bb7 of Ebdim7; the E on beat 3 is not in the chord, so the chord waits until beat 4. Timing a passing chord to the melody is normal practice, not a compromise.
• Bar 4, Db7#11. The tritone sub of G7. The melody's G is the #11, which is exactly why tritone subs are written with #11: the root of the chord they replace is their #11. Bass D–Db–C.
• Bar 5, Gb7#11. The tritone sub of C7 (V7/IV from version A). The melody's C is again the #11 of the substitute, and the bass falls by a half step into the F of bar 6.
• Bar 6, Eb9. The tritone sub of A7 (V7/ii), pointing at the Dm7 of bar 7. The melody's G is the 3rd of Eb and the F is its 9th. Bass F–Eb–D.
• Bar 7, Db7b9. The tritone sub of G7 once more, now with the melody's D as its b9. Bass D–Db–C into the final tonic.

The complete bass line is C–C#–D–G–E–Eb–D–Db–C–Gb–F–Eb–D–Db–C. Apart from the untouched bar 2 and one tritone leap into the Gb, it moves entirely by half step. Play the lower voice alone and you will hear a line a bass player would be pleased to walk.

Because the chord symbols here are the real work, here is the lower voice on its own as a comping étude with the chord-tone check switched on, so that you can see that every shell is what its symbol says it is.

\tempo 110
.
\ts 4 4
:2 (8.6 7.5 9.4){ch "Cmaj7"} (9.6 9.4 9.3){ch "C#m7b5"} | (5.5 3.4 5.3){ch "Dm7"} (3.6 2.5 3.4){ch "G7"} | (0.6 0.4 0.3){ch "Em7"} (6.5 7.4 5.3){ch "Ebdim7"} | (5.5 3.4 5.3){ch "Dm7"} (4.5 3.4 4.3){ch "Db7#11"} | (8.6 7.5 9.4){ch "Cmaj7"} (9.5 8.4 9.3){ch "Gb7#11"} | (8.5 7.4 9.3){ch "Fmaj7"} (6.5 5.4 6.3){ch "Eb9"} | (5.5 3.4 5.3){ch "Dm7"} (4.5 3.4 4.3){ch "Db7b9"} | :1 (3.5 2.4 4.3){ch "Cmaj7"} |

Reharmonisation C: modal interchange and constant structure

The third version goes for colour rather than motion: chords borrowed from C minor, a constant-structure slide, and a backdoor ending. The chords are | Cmaj7 | Dm7 G7 | Am7 Abmaj7 | Dm7b5 G7b9 | Cmaj7 Dbmaj7 | Fmaj7 Fm6/9 | Bb9 | Cmaj7 |. Bars 1 and 2 are untouched so that the first borrowed chord, in bar 3, arrives as a surprise.

\tempo 84
.
\ts 4 4
\voice :4 9.3 8.2 :2 7.1 | :4 5.1 6.2 :2 3.2 | :2 3.1 :4 5.2 5.3 | :4 3.2 6.2 :2 3.1 | :4 9.3 8.2 :2 8.1 | :2 10.2 :4 8.2 6.2 | :4 3.2 5.3 :2 3.2 | :1 1.2 |
\voice :4 (8.6 7.5 9.4){ch "Cmaj7"} r (8.6 7.5 9.4) r | (5.5 3.4 5.3){ch "Dm7"} r (3.6 2.5 3.4){ch "G7"} r | :2 (5.6 3.5 5.4){ch "Am7"} :4 r (4.6 3.5 5.4){ch "Abmaj7"} | (5.5 6.4 5.3){ch "Dm7b5"} r (2.5 3.4 1.3){ch "G7b9"} r | (8.6 7.5 9.4){ch "Cmaj7"} r (9.6 8.5 10.4){ch "Dbmaj7"} r | (8.5 7.4 9.3){ch "Fmaj7"} r (8.5 6.4 7.3){ch "Fm6/9"} r | (1.5 0.4 1.3){ch "Bb9"} r (1.5 0.4 1.3) r | :1 (3.5 2.4 4.3){ch "Cmaj7"} |

• Bar 3, Abmaj7 (bVImaj7). Borrowed from C minor, placed on beat 4 under the melody's C, which is its 3rd. The bass moves A–Ab–D, and the Ab is the first flattened note the listener hears.
• Bar 4, Dm7b5 and G7b9 (iiø7–V7b9). The borrowed half-diminished ii and a dominant with the b9. The melody's D and F are the root and b3 of Dm7b5; the G is the root of G7b9. The shell under the Dm7b5 is root, b5, b7 so that the Ab is actually heard, and the G7b9 is the rootless shape from lesson 3 (3rd, 7th, b9) with the melody's G as the root on top.
• Bar 5, Dbmaj7 (bIImaj7). The melody's C is the major 7th of Db. This is the Phrygian chord from lesson 4, and it is also a constant-structure move: the Cmaj7 shell slides up one fret with the melody holding still. It has no functional job; it is there for colour, and it leads into the Fmaj7 of bar 6 by a chromatic-mediant relationship (Db and F are a major 3rd apart, lesson 5).
• Bar 6, Fm6/9 (iv). The minor plagal cadence: IV becomes iv under the melody's G and F. The G is the 9th of Fm6, hence the symbol; the F is the root. The shell is root, b3, 6.
• Bar 7, Bb9 (bVII7). The backdoor dominant for the whole bar instead of ii–V. The melody's D is its 3rd and the C on beat 2 is its 9th, so the one shell (root, 3rd, 7th on strings 5–4–3) covers the bar, and the bass line F–Bb–C closes the tune through the back door.

Play the three versions back to back. Same melody, three bass lines, three characters: the first is a swing tune, the second is bebop, the third is something you might hear on a modern trio record. None of them is the "right" one. On a gig you would use version A behind a singer at a medium tempo, version B for the last chorus of an up-tempo arrangement, and version C for a ballad or a solo guitar intro.

Guidelines

A short list of things that hold true however far you take this:

• The melody wins. A beautiful chord that clashes with the tune is a wrong chord. Check every note on every chord change, and check the notes on the weak beats too, because a half note is long enough for the listener to hear a clash.
• Keep the first and last chords. Reharmonise the middle; let the tune start and end where the composer put it, unless you are deliberately writing an alternative ending.
• Change the function or the colour, not both at once. Version A changes the function of chords and keeps the colour diatonic; version C keeps the functions and changes the colour. Doing both in every bar produces mush.
• Leave some bars alone. The chord you did not change is what makes the one you did audible.
• Write the bass line first if the goal is motion. Decide where the bass goes, then find the chords that put it there. Chromatic bass lines come from passing diminished chords, tritone subs and rootless 7b9 shapes; bass lines in 5ths come from secondary dominants and related iis.
• Write the colour first if the goal is mood. Choose the borrowed or constant-structure chord you want to hear, find the melody note that allows it, and place it there.
• Respect the tempo. Six chords in two bars works at 80 bpm and not at 240. Fast tunes take one substitution per phrase; ballads take one per beat.
• Reharmonise for the band you are in. With a bass player, you can imply a chromatic bass line and let the bass choose to follow or not; alone, you must play it. With a pianist, agree on the changes or keep them to the last chorus.

Exercises

1. Analyse. Write the Roman numerals and the melody-note degrees of the original melody, then of all three reharmonisations, in a table. Check every entry against the chord tables in this lesson.
2. Play all three as written, then play each one's lower voice alone as a comping part with a metronome.
3. Transpose. Move the melody and version A to F and to G. Then version B to F (the bass line should still move by half steps). Then version C to G.
4. Combine. Write a fourth version that uses the best bar from each of the three. Keep the first and last chords.
5. A tune you know. Take an eight-bar phrase of a standard, write out its melody notes on each chord change, and apply exactly one device per two bars. Record it. Then try a second version with a chromatic bass line.
6. Chord melody. Play version C with the melody and chords as a solo piece, adding a bass note on beat 1 of each bar where the shell does not already give you one. This is the method of Module 13 in miniature.

Quiz