In this article we're going to tackle the beautiful jazz standard "When I Fall in Love," solo piano. We're going to look at a very common reharmonization technique that jazz pianists use on this tune. "Reharmonization" means to take the underlying original harmony and tweak it in a way that introduces new chords. The challenge, as jazz arrangers, comes in trying to make sure that the original melody remains fully intact and that the new chords that we will introduce will not obscure the melody. After all, the melody is so important because it is the element of the song that is most recognizable to the listener's ears.
The Original Melody and Harmony
Let's start by checking out the first two measures of "When I Fall in Love." We're going to look at this song in the key of Eb.
Now let's analyze the harmony that we see here. In the key of Eb we have the 'I' chord (Ebmaj), followed by the 'V/ii' chord (C7), then the 'ii' chord (Fmin7), and finally the 'V' chord (Bb7). If we flesh this out across both treble and bass clef, we could get something like this:
Reharmonizing - Substituting the Original Chords
The important first consideration before substituting any chords is to understand how the original harmony WORKS! The chords above are what we call "functional harmony," meaning that they resolve from one chord to the next. The Eb major chord makes sense because it is, after all, the 'I' chord - the chord that simply states the home-base key. The F minor and Bb7 chord in measure 2 are referred to as diatonic chords, which means that these chords are naturally-occurring in the key of Eb major. So the only chord in the first 2 measures that requires some extra explanation is the C7 chord in measure 1. What is it?
The C7 chord is not diatonic to the key of Eb major. It is what is referred to as a secondary dominant chord, meaning that it is a dominant chord which comes from outside of the key signature and pulls us to the F minor chord. Notice that the C7 chord pulls us (in a 'V' to 'i' resolution) to the F minor chord.
We're going to leave the chords in measure 2 alone and focus on the chords in measure 1. First, we're going to leave the Eb major chord alone. Next, we're going to move the C7 chord over one beat, so that it occurs on beat 4. After all, this is the chord that leads us to F minor, so it's important that we not remove it completely.
What two new chords will we add? We're going to add extended dominants (aka sequential dominants) that will lead us to the C7 chord.
What we've done here is move in fifths - from Eb, down a fifth to Ab7, down a fifth to Db7, and then down... a half-step to C7? The C7 actually takes the place of the Gb7 chord, which would be the next chord in our sequence after Db7. But instead of Gb7, we use the tritone substitution which just happens to be... C7! In the end, we get a reharmonized, robust, more pro-sounding arrangement.
If you want the full arrangement, check out the full lesson of "When I Fall in Love" complete with many more reharmonization examples.