The Following is a basic blues riff in the key of "A". This fiff is made up of two note chords shown on the tab staff. The chord names above the staff are there as a reference to show you what the basic harmony is while you play along.
This riff should sound very familiar, it's used more than any other blues progression. A lot of rock and blues classics are played entirely with this one riff repeated over and over. It is made up of 12 measures (or bars) of music called the 12 bar blues, in other words a blues progression consisting of twelve repeated bars of music.
You can click on the tab images to enlarge it.
Blues is played with a shuffle feel, also called a triplet feel. This example was written in eighth notes and the second eighth note of each beat should lag a little bit. This is refered to as a triplet feel because the beat is actually divided by thirds, counted as if there were threee eighth notes per beat instead of two. The first part of the beat gets 2/3 of a beat, the second part gets 1/3.
This 12-bar blues riff is also nan example of a I - IV - V (one-four-five) chord progression. The roman numerals refer to the steps of the scale, relative to what key the music is in. So, the A chord is the I chord (also called the tonic). The D chord is the IV chord (also called the subdominant) because in the key of A, D is the forth step in the scale. Finally, the V chord (or dominant) is the E chord, because E is the fifth step of the scale in the key of A.
The I - IV - V chord progression is the most common progression used in rock or blues. It's the foundation that all rock and blues was built on and has evolved from. There are many variations, but songs such as "Johnny B. Goode," "You Really Got Me," "Rock nad Roll," "I Love Rock and Roll" and "Sympathy for the Devil" are all bases on the I - IV - V.
Have fun with the bassic blues progression and learn to play it in other keys as well. It will open your eyes to many songs.