In this article I am going to be going over the basic understandings of the circle of fifths in terms of building a harmony in your music. To start let me share my thoughts on Harmony and what it is. To start we have to go to the very route of music and why it sounds good.
Music is perceived subconsciously by humans as "good sounding" by it's abuility to create and hold complex ratios and mathmatical similarities. That is what separates it from objects just clanging together. All notes are based on ratios. All scales are organizing the ratios in such a way that there is perceived order. When you play a C first you are saying that is the root, or the lowest point on the scale. Then you build other notes that are in ratios and you get chords.
Music is that play between this perfect good sounding ratios and Tension which is ratios that work but aren't perfect. This tension creats interest as well as can be resolved to add release in the listener. Harmony is the basic ratios going back and forth from perfect to tense to perfect.
Wiki describes Harmony as: Harmony involves chords and their construction and chord progressions and the principles of connection that govern them. So by having those chords progress from the center perfect to tense and back you create a full basic sound to build the rest of your music from. The difference of the harmony and melody is that the Harmony creates that tonal base. It is setting up the ratios and landscape that the melody then drifts on. A lot of electronic music lacks really good harmony and can add a real depth to your music with it.
As an example lets look at the Major scale. Lets say the root is C. C is ground zero and will always sound great, but will get old. The notes and chords next to it on the circle of fifths sound great. IV is pretty good, and V really wants to go back to the Root, or I. So you can just go from I to IV to V and it will sound good.
The others are getting further and further from the root and want to go back to it, but sound more and more tense. You can use that to create interest. Example is go: I, VI, iii V, and back to I if you repeat this you have a great harmony that sways in and out and resolves back.
After you have a harmony it is really easy to see those notes used and build your melody.
One resource I have made available is my Library of chords that goes through every key and draws out all the chords. This way you can quickly and easily write your melodies in ableton. Check out the video below about the Library of Chords.