If you are in C Major, use an Abmaj7 (from C minor) instead of an F major.
Reharmonization is as much about the bass line as it is the chords. Aim for smooth voice leading or intentional chromatic steps. Reharmonization Techniques
The "engine" of a G7 is the tritone between its 3rd (B) and 7th (F). A Db7 uses these same two notes (the 3rd is F, the 7th is Cb/B), creating a smooth, chromatic bass descent to the target chord. 3. Secondary Dominants If you are in C Major, use an
Moving the same chord shape (like a Minor 9th or a Quartal voicing) in parallel with the melody, regardless of the key signature. This creates a modern, "shifting" sound common in Impressionism and modern jazz. 6. The "ii-V" Expansion The "engine" of a G7 is the tritone
The most important rule is that the new chord must not contain a note that "clashes" (usually a minor 9th interval) with the melody note being held.
This involves "borrowing" chords from a parallel mode, usually the parallel minor.
Replacing a IV (F) with a iv (Fm) or a bVII (Bb7). This adds a "darker" or more cinematic quality to a major-key melody. 5. Line Cliché and Constant Structure