So while some songwriters start with lyrics first, others start with the instrumental part first. If you write with a guitar, it’s not uncommon to start by strumming a guitar and stumbling on a cool chord or riff. Or if you are a singer who doesn’t play an instrument, you may have to develop bits and pieces that are brought in by your collaborators/cowriters.
Either way, here’s a bullet-proof way to start writing a melody on top of a chord progression. It’s real simple: analyze the notes used in the chords, and hit one of them when the chord arrives.
So here is a very simple example:
|Notes||G, B, D||D, F#, A||E, G, B||C, E, G|
So in the example above, you start constructing a melodic line by picking out a note from each chord and make sure you land on it when that chord arrives. Of course if you just sang one note per chord that’ll be a very static, boring melody so you can fill in the gap with other notes, and those filler notes don’t have to be one of the chord tones. Now don’t get me wrong, by “filler notes” I don’t mean that those are unimportant notes in the melody. But in this context we consider those to be the connectors between dots in the game of connect-the-dots. When the chords are basic triads there are only three notes, but between them and different octaves and you’ll still get a wide variety of possibilities.
Of course, this is just a starting point — if the resulting melody ends up sounding too predictable or plain, by all means stretch the rule, break them here and there. Also consider that rhythm is a very strong element of a melody — even if the notes are predictable, you can add plenty of interest by varying the rhythm. But even without trying too hard, when the riff/chord progression is less traditional, just composing a melody that “fits” the underlying music will still be pretty effective.
Once you get used to this concept and do it a few times, you’ll start to do it without thinking too hard about it. Whether you can “name” the chord is not the point here, you just have to pick out one/some of them, to start.
I have a song called “Can You Love a Landmine?” which has a riff relying on these chords:
|Notes||F#, A, C#, G#||A, C#, E, B||E, G#, B, D, F#, A#|
When I wrote the melody I actually didn’t bother mapping out notes like above. But when I analyzed the notes I did use, I realized I started with G# on the first chord and landed on A# and F# on the last chord. Without even thinking I was capitalizing on the colorful notes in these chords instead of the notes from the base triads.
The advantage of knowing this approach is that once you become familiar with the concept, no riffs/chord progressions will scare you. It doesn’t matter how unorthodox, weird or unfamiliar the material is. This approach will always get you started.
Incidentally, this is the exact same approach one uses to start to learn how to improvise. Which makes sense — because improvising (as in improvised solos) is essentially creating a melody over a foundation of other instruments, on the spot.
So in conclusion, whenever you have to write a melody over existing music and are stumped as to where to begin, just start by picking out notes in the chords. It may seem arduous at first but your ear and brain will adjust and you’ll be able to do it without thinking eventually. Even then, when something foreign comes along, always fall back to this approach — pick out the notes in the chords. It’ll always get you unstuck.