Arranging and reharmonising a tune

Arranging is composing with a safety net: the melody already exists, and everything else — harmony, texture, introduction, countermelodies, variations — is yours. It is one of the best exercises there is, and it’s how most great composers learned: Liszt arranged songs, Bartók folk tunes, Ravel Greek melodies. We are going to take a public-domain song that everyone knows, “Au clair de la lune”, and turn it step by step into a real piano piece.

Step 1: check the melody and lay down basic harmony

First, make sure you have the exact melody: many versions floating around are wrong. Play it, sing it, count the bars. Then lay down the simplest possible harmony, with only I and V: this is your starting point, your “reference version”.

M:4/4
L:1/4
Q:1/4=100
K:C
"C" c c c "G" d | "C" e2 "G" d2 | "C" c e "G7" d d | "C" c4 |]

Step 2: choose a texture

The same chord can be presented in a thousand ways (revisit the lesson on left-hand patterns). An Alberti bass immediately gives the flavour of a classical sonatina. Notice the G chord written B–G–D–G: we choose the inversion that moves least from the previous chord.

M:4/4
L:1/8
Q:1/4=88
K:C
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
[V:RH] c2 c2 c2 d2 | e4 d4 | c2 e2 d2 d2 | c8 |]
[V:LH] C,G,E,G, C,G,E,G, | C,G,E,G, B,,G,D,G, | C,G,E,G, B,,G,F,G, | C,4 [C,E,G,]4 |]

Step 3: add a countermelody

An arrangement comes alive when the left hand stops merely accompanying and starts to sing too. Here the bass draws a line in half notes, often in contrary motion to the melody. As a result the harmony enriches itself: A minor, D minor with F in the bass… and the melody hasn’t changed by a single note!

M:4/4
L:1/4
Q:1/4=84
K:C
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
[V:RH] "C/E" c c "C/G" c "G" d | "C/G" e2 "G/B" d2 | "Am" c e "Dm/F" d d | "C/E" c2 "C" c2 |]
[V:LH] E,2 G,2 | G,2 B,,2 | A,2 F,2 | E,2 C,2 |]

Step 4: vary the repeats

A song repeats; an arrangement must never repeat identically. On the repeat, decorate the melody (passing notes, neighbour notes, dotted rhythms), change register or texture. Here is an ornamented version: the main melody notes are still there, on the strong beats.

M:4/4
L:1/8
Q:1/4=88
K:C
"C" c2 cB c2 "G" d2 | "C" e3 f "G" e2 d2 | "C" c2 e2 "G7" d2 Bd | "C" c8 |]

Reharmonising: changing the lighting of a melody

To reharmonise is to keep the melody intact and change the chords underneath. The same note can belong to several chords: C is the root of C major, the third of A minor, the fifth of F major, the seventh of D minor 7… Here are the most useful substitutions:

Let’s compare. Here is “Au clair de la lune” reharmonised: a bass line descending chromatically (A, G, F, F♯), a secondary dominant D7 (V/V) pushing towards G, then E7 with G♯ in the bass rising to A minor. Exactly the same melody as in step 1… and yet it sounds like a nostalgic ballad!

M:4/4
L:1/4
Q:1/4=72
K:C
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
[V:RH] "Am" c "Am/G" c "F" c "D7/F#" d | "C/G" e2 "E7/G#" d2 | "Am" c e "Dm7" d "G7" d | "C" c4 |]
[V:LH] [A,,A,] [G,,G,] [F,,F,] [^F,,^F,] | [G,,G,]2 [^G,,^G,]2 | [A,,A,]2 [D,,D,] [G,,G,] | [C,,C,]4 |]

Your workshop

1. Choose a public-domain tune you know perfectly (“Au clair de la lune”, “Frère Jacques”, “Scarborough Fair”…) and check it against the site’s score (Au clair de la lune, When the Saints Go Marching In).
2. Enter it in the ABC editor with a basic I–IV–V harmony (one or two chords per bar).
3. Write a two-stave piano version with a left-hand texture of your choice (Alberti, waltz, arpeggios).
4. Add a two-bar introduction and a left-hand countermelody for the repeat.
5. For a third statement, reharmonise at least four chords: a vi substitute, a ii, a secondary dominant and a chromatic bass. Try the progressions out in chord progressions.
6. Self-check: is the melody still singable and perfectly recognisable? Does each statement bring something new?