To discuss chord progressions, we label each note of a scale with a roman numeral, for example:
By far the most common chord progression in blues, pop and rock music is the I-IV-V progression. This means if we were playing in the key of A major, the progression would be A-D-E (the I, IV and V chords of the A major scale).
We can transpose this to any key by taking the 1st, 4th and 5th notes of any scale and playing their appropriate chord. These chords are known as Primary chords, as they are the strongest chords of the scale. All three are major chords.
12 Bar Blues is a famous I-IV-V chord progression, and is a standard blues progression which is used extensively in rock and pop music as well. Here is an example in the key of A major. Strum each chord for the number of bars indicated, keeping a steady count in your head.
The V chord is dominant so we play dominant 7. Quite often in blues the I and IV chords are played as dominant 7 chords as well. This 12-bar chord pattern is repeated as often as necessary. This chord structure is very common in the music of Eric Clapton, Stevie Ray Vaughan, BB King, and of course all the old blues greats. Variations abound on this, however. Each chord can be used in any sequence. For example try I-V-IV as a chord progression, or I-IV-I-V.
Another common trick is to take the I-IV-V progression and add the relative minor chord (VI). This creates quite a strong progression with a lot of feeling. Here is an example in the key of A:
Again the V chord is normally played as dominant, but can also be played as a straight major chord as well. This type of progression is used in songs such as 'D'yer Maker' by Led Zeppelin (in the key of C), and many '50's rock and roll songs. In fact, this progression has come to be known as the 'doo-wop' progression, as it features heavily in what is referred to as 'doo-wop' music of the 1950's.
Variations are also quite common on this theme. Try I-VI-I-V to get 'Wonderwall' by Oasis, or I-V-VI-IV to get 'Beast of Burden' by the Rolling Stones, or 'Let it Be' by The Beatles.
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