Ok, I want to start writing songs. I want to write songs that basically use 4 chords for the verses. I have two questions...

1. How do I change from a 4 chord progression for the verse to another 2/3/4 chord progression for the chorus. I need to know how to pick two progression that will fit together, or will all progressions fit?

2. Is there a site/page that lists ten or twenty or even all possible chord progressions. Well at least simple 3 or 4 chord progressions. And if it lists chord progressions that it "fits" with as well.

The first song I want to write is a really sad song, so I want to fit it to a 4-chord progression in a minor key, that switches to a 2-3 chord progression riff for the chorus. I need to understand the theory behind it, but a list of heaps of progressions for songwriting or something similar would be great!

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What really helps with writing 2,3 or 4 chord progression songs is knowing what chords are in each key.
The root note in a major scale has a major chord
The 2nd note has a minor chord
the 3rd note is a minor chord
the 4th note is a major chord
the 5th note is a major chord
the 6th note is a minor chord
and the 7th note is a diminished chord
so in C: C, Dm, Em, F, G, Am, B dim

you can apply this to any key and if you want a sad song for instance you might focus on the minor chords in the key

but the best way to learn anything in music is to use your ear!

Hello.
Try checking out a "circle of fifths". Easy way to find chords for I-IV-V progression. It's used typically for 12 bar blues, but kind of shows a general chord relationships.
Hope it helps.

Look at my post at chord progression thread. It should help a little. This is not complicated.

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