The basics of songwriting can be categorized into 4 sections.
Song structure, chord progression, lyrics, and melody.
This order is not a set in stone way of writing a song.
For me, each song has come about in different ways, some processes more than others.
Sometimes I get a melody stuck in my head.
Sometimes I think of a lyric line that leads the way to becoming a whole song.
This is the second part to 'Basics of Songwriting'.
Chord Progression: Chord progression is a set of chords that make up the harmonic structure of songs.
Generally, each verse shares the same chord progression and each chorus share the same chord progression.
For example, I can use the key of 'G Major' (you can go here for a deeper explanation) with the chord pattern G - D - Em - C for my verses and G - Em - D - C for my choruses.
There is only one bridge so we can make it unique by starting it with a minor chord.
An example would be Em - C - D.
If we used these chords with our popular radio friendly song structure, it would look like this.
intro (we'll use the chords from the verse): G - D - Em - C verse1: G - D - Em - C chorus1: G - Em - D - C verse2: G - D - Em - C chorus2: G - Em - D - C bridge: Em - C - D chorus3: G - Em - D - C Depending on how your lyrics and melody work out, you might have the set of chords played more than once through each section.
Songwriting tip for chord progressions: Sometimes, songwriters puts in a surprise chord that breaks the normal progression pattern.
For example, let's look at the bridge.
It starts with an E minor chord.
Minor chords are dark sounding and feels deeply emotional and you might want to have a chord that sets up the bridge.
You can change the last C chord of chorus2 into an Am.
The Am chord sets up the mood for the coming Em.
This isn't an aimless change of a major chord to a random minor chord.
C and Am are actually relative chords.
Quick lesson on relative chords: Relative chords are a third from each other.
So for example, in the key of G Major, Am is a third below C: Am -> B -> C.
In the same way, Em is related to G: Em -> F#dim -> G.
Also, Bm is related to D: Bm -> C-> D.
For more on keys and their relative minors, you can see a list here.
Back to songwriting tip: Most of the time, you don't have to change a melody when you change one chord to it's relative chord because they share common notes.
For example, C and Am share the notes C and E.
If a change in melody is necessary, it is not a big deal because it adds a small twist of variety of a song which can help make the song feel fresh.