Although instrumental accompaniment is almost universal in the blues, the blues is essentially a vocal form. The Blues are rather lyrical rather than narrative.
Blues singers are expressing feelings rather than telling stories. The emotion expressed is generally one of sadness or melancholy, often due to problems in love or struggle. To express this musically, musicians of the blues genre would use techniques such as sustaining a single syllable across several pitches, rhythmic techniques such as syncopation and instrumental techniques such as bending or chocking guitar strings on the neck of the guitar strings to create