Think of it this way. Chord progressions - Move the song through the verse structure. A verse brings up a thought, discusses it, reaches a conclusion and brings this thought to and end. Time for the second verse where a new thought is brought forward discussed - a conclusion is reached and the thought is then brought to a close. Time for the chorus. Same thing or it can be a little different. Let's say the same format is used in both the verses and the chorus.
This song is in the key of C. C has these chords:
C, Dm, Em F, G, Am, Bdim, C octave. To identify the chords we give them Roman Numeral names.
I,,, ii,,, iii,, IV, V, vi, viidim, I
C, Dm, Em, F, G, Am, Bdim, C
Notice the upper case are Major chords and the lower case are minor chords. Three major, three minor and one diminished chord in every key.
All chords within a specific key will sound OK with every other chord in that same key. But, the chords within a key do like to go to certain other chords and in doing so they move the progression through the verse structure.
Verse starts lets say with the tonic I chord (it does not have to start with the I chord let's just say it does for our example). Then moves to the discussion part of the verse using the IV chord. The verse now reaches a climax with the V or V7 chord. Since we have reached climax if we keep messing around it gets anti-climatic so we should now end this thought or verse - by returning to the tonic I chord. I IV V7 I
Let's say we have a four line verse First two lines start and finish one complete I IV V I progression and this same progression is used in the last two lines of the verse. So we have two complete progressions in each four line verse.
Understand it does not have to be this way. This is just a generic example.
Well that's only three chords what do all seven like to do?
The I or tonic chord can go anywhere within the progression it wants to go, however, when you go to the I chord you have resolved any tension you have built - are you ready to resolve, if not don't go to the I chord just yet.
The ii chord is called a Sub-dominant chord it's task in life is to move to a dominant chord. The IV chord is also a Sub-dominant chord so it too wants to move to a dominant chord. Both the ii and the IV can substitute for each other.
The iii chord is called the minor mediant chord. It likes to lead to the vi chord.
The IV as mentioned above is a sub-dominant chord and wants to move to a dominant chord.
The V is the dominant chord and it's task in life is to move to the tonic chord (I) as quickly as possible. The viidim chord is also a dominant chord and it's task in life is to also move to the I tonic chord, however, the viidim chord is not only a dominant chord it is also the minor leading tone diminished chord and it also likes to lead somewhere and take a more leisurely trip to the tonic I chord. So if you want to reach resolution quickly use the V7 chord, however, if you want to take a more leisurely trip - like in a turn-a-round then use the viidim to the iii then the vi then the ii or IV to the V7 to the I. That is the classic turn-a-round, i.e. viidim-iii-vi-ii-V7-I.
The vi is the relative minor chord. It likes to move to a sub-dominant chord (ii or IV).
The viidim was discussed above.
So you start your verse with a I chord what is the quickest way back to the I chord? Through the V7. Yep, and a I-V7-I is a good progression to use when you get lost and need to kill some time till you figure out where the rest of the band is.
What about a I IV V I progression? Used all the time.
What about a ii V7 I progression? Used all the time in jazz.
What about a I vi IV V I progression? Well the vi likes to go to a sub-dominant chord so yes this works great. In fact it's called the ice cream progression as it is/was used in early sock rock music all the time.
If you let the chords move where they like to move good things happen. Remember I said you do not have to start a verse with the I chord - well you should end each verse with the I chord. Why? By moving to the I chord you resolve all tension and the verse (phrase) is back at rest. If you did not end with the I chord its like a run on sentence. Think of the I chord at the end of the verse as the period.
More info at
www.musictheory.net -- Lessons then go to Common Chord Progressions.
Make yourself a cheat sheet and keep this handy, it only takes a little while till this is embedded in your memory.
Have fun.
