Features of blues songs

The most common chord structure uses three chords – the tonic (chord I), the subdominant (chord IV) and the dominant (chord V). In the key of C this would be:

Phrase 1C (tonic)C (tonic)C (tonic)C7 (tonic)
Phrase 2F (subdominant)F (subdominant)C (tonic)C (tonic)
Phrase 3G (dominant)F (subdominant)C (tonic)G (dominant) to repeat or C (tonic) to finish

There are many variations on the above structure. Sometimes 7th chords are used (the same chords with an added 7th). The 12-bar blues form the basis of R&B (rhythm and blues), rock and roll and jazz music.

Blue notes

Compared with the major scale, some notes, known as blue notes may be flattened by a semitone or ‘bent’ by a smaller interval. Blue notes are usually found on the third, fifth or seventh degree of the scale.

Guitarists can ‘bend’ the notes out of tune by pushing the strings sideways. A bottleneck is sometimes used to slide up and down the guitar strings. Both effects sound like a vocal cry.

There is bottleneck guitar in the song Travelling Riverside Blues by Robert Johnson.

Travelling Riverside Blues