This article is an introduction for anyone who wants to learn more about composing music. An introduction should be treated for that it is: a beginner’s course. So do not expect to learn all there is about composing by reading this.
A song usually consists of many things in which harmony, melody and lyrics (if it is not instrumental) are some of the main components.
Harmony in music could be described in many ways. You can call it the mood or atmosphere of the song. A concrete example of harmony in music can be an instrument’s accompany to a singer. Whatever the ingredients are the harmony is collaborating with the melody.
The melody is the most distinct part of the music. It is the melody you often remember from a song and maybe recapitulate afterwards by whistle it.
Combine harmony and melody
The order in which harmony and melody are created can vary between composers. The art of combining harmony and melody is done with talent, experience and some guidelines. This article cannot offer talent or experience, but it can give you some of the guidelines.
Two fundamental elements in composing music are scales and chords. Then creating a piece of music the knowledge of scales is indeed helpful. You should not be bound to a certain scale and let it limit your creativeness, but you should be aware of the contexts of scales. Maybe you are sitting in front of a piano and do not have a clue that keys you should press down for making it sound alright?
You know which the easiest way to start composing on a piano is? Just play exclusively on the white keys!
Doing this, you are playing in the scale of C Major and therefore you do not hear any dissonance. You can use the notes in the scale for both harmony and melody. Use your left hand for chords (this site focus on scales, if you want to learn chords use your search engine or visit Pianochord.org) and your right hand for the single notes.
Of course, this is a simple approach to composing, but it is a start.
The song structure and related areas
When you are composing a song there is often enough to stay in one or two keys throughout the song. A typical song starts in one key and then stays in it, or, changes key somewhere in the song and most often change back to the original key before the end.
In popular music a typical song structure could look something like this: 1) Intro; 2) Verse; 3) Chorus; 4) Verse; 5) Chorus; 6) Bridge; 7) Verse; 8) Chorus; 9) Outro.
The verses approximately consist of 3-6 lines and usually with different lyrics. The chorus tends to use fewer lines and often repeat the same lyrics. Needless to say: the harmony and melody should change going from verse to chorus.
So you got a melody and need some harmony?
Let says you have a melody, but do not know how to add harmony to it. There is more than one way to create harmony; two common ways are with counterpoints or chords. We are taking the easiest route and choose chords.
Once again, there is more than one way to add chords to a melody. Because this is only an introduction in music composition we are satisfied with two rules which are: 1) add chords in which the second or the third note is the same as the melody note; 2) don’t add chords to every melody note, one or two in every bar is often advisable.
Concerning the motion: the harmony can be parallel or contrary to the melody line. To think about the motion in this way can be helpful.
Tonic, subdominant and dominant
Many songs include only three chords and they are often the tonic, the subdominant and the dominant (see Theory - Scale Degrees for further information). The dominant chord often has a septima and it revolves into the tonic. An example could look like C - F - G7 - C.
Ending it all
When you reach the end of the song a common method is to shorten the interval between chords. This accomplishes a breaking effect. The name that is often used for the chord progression at the end of a phrase or song is cadence. One example of a cadence in major is: C - F - G7 - C. A cadence in minor could be: Am - Dm - E7 - Am.
The Circle of fifths
When composing music it serves you to have a visualization of the relationship between chords and scales.
A common visual way to present this is by the Circle of fifths. It is called so because every note is a perfect fifth away from the next. A composer knows, for example, that a D7 chord resolves into G, a G7 chord resolves to C and so on.
The circle also shows the relative keys. A minor is, for example, relative to C major. It means that you can play the same notes as in C major, but starting from the note of A. By doing so you will get a more melancholy sound. Compare major and minor scales and you will notice the relationships.