This is one of the hardest parts about music production, one that if it was easy, there'd be a new hit song every day. Making a catchy melody is really difficult. People often jump to try and get the most dazzlingly complex melody that will catch people's ears, but that shouldn't always be the case.
The thing is, most modern pop music is incredibly formulaic. Remember a few years ago when Axis of Awesome hit the spotlight on Youtube, playing their Four Chord Song? To many, it revealed how unoriginal most modern music was, playing the same four chords and making "every" song ever fit to it.
To me however, I think the main thing it demonstrates is the amount of variation that can be created from such simple elements. If you haven't already, give it a listen and you will see how much diversity there still is within the songs. This is down to the melodies.
So let's not worry about add9 or diminished chords in this article, nothing too complex. There is a working formula let's look at that first and then from there, you can do your experimenting.
So, how do you create a new melody from this four chord template? The first thing is to highlight the notes in each chord. If a note in the melody corresponds with one in the chord, it will sound nice. Likewise, to perhaps a lesser degree, the rest of the notes in that key signature will also sound good with the chord.
So here in my DAW, I've outlined the chord progression that I want to use. The very first thing to do is identify the notes. These are your main notes. The next step would be to split them at each beat, this means you can delete bits and start forming a melody.
Start deleting a few notes and you will see a melody instantly start forming. Consider which notes are present in the current chord and in the chord about to be played, maybe that would be a good "transition" note between chords, it's not a rule to always follow (as seen below). Likewise, people enjoy an upward movement, so consider following that.
You can now see a melody taking place. Chances are, it's a bit boring. So let's start moving the notes about so they don't all fall on the beat. You could employ a "shuffle" quantisation, but let's for now just move them around.
I'm not following any rules here beyond keeping the "chords" within their sections. Now we have some movement within the beats, there is some off beat action which sounds nice. Let's start adding some notes that don't directly fit into the chords. I'm a big fan of sus4 chords so let's make the first chord change to a sus4 midway through the bar.
I added the 4th (encircled in green)
Small additions of this are really nice. Think about the song Titanium, by David Guetta and Sia, the chorus changes from a minor chord to the sus2 as she sings through the word Ti-ta-ni-um, as seen below in Ultimate Guitar's chord guide.
This creates a movement within the chord, while retaining the chord itself. Let's look at more notes we can add. You will see that all these notes are falling within one octave. By adding bass and higher notes to the melody, conservatively, you can bring more interesting content into the sound of the melody.
You can see here the addition of a few bass notes, this gets tricky, the more busy it is, so make sure to change the velocity of each note hit so they aren't all full volume. Bear in mind, at this point, we are just laying down the rough movement of melody. Many of these notes are not going to be played by one instrument. This is just to see if the notes work together harmonically.
Which brings us onto the next stage. Now is the time to dish out each note to it's respective instrument. I am going to take the low notes and put them on a bass synth.
The bass part.
Next, I'm going to copy the main melody to a synth, I'm going to make it a soft plucky synth, find a nice preset and tweak to fit the sound of you melody.
Now all we need is a lead sound, this would normally be a voice singing over, but in this case, I am going to use a synth. Pick some notes from the melody that form a nice simple lead progression, just play one note at any time (like a singer would) and there you have it.
These are the notes I picked for instance.
Just load them onto a synth sound of your choice and there you go. For the sound, I went for, I added a nice delay effect onto the plucky and lead synth and it adds a bit more of a lively sound. Below is the tracks, each with their notes tracked out.
You will see that on the lead synth, the MIDI notes are overlapping, however since I set the synth to be monophonic, it will only ever play the most recent hit note at any time. I also added a portamento glide on to make the note transitions sound nice.