Taking Measure of the 12-Bar Blues

Most blues songs take the form of the 12-bar blues, so called because it consists of 12 bars (i.e., measures) of four beats each. There are three sung lines, each one fitting into a four-bar section. Almost always, the first line is sung twice, and then the thought is completed or answered by the final line.

A usual blues verse, with the chord changes in the key of E, looks like this:

Trouble last night and trouble the night before
Trouble last night and trouble the night before
Trouble in my home and trouble knocking at my door.

The words fit against a chord structure that you would strum out like this, with each slash representing one beat:

Represented in music, the melody and strumming looks like this:

12-Bar Blues