The blues genre is based on Memphis-Blues the blues form but possesses other characteristics such as specific lyrics, bass lines and instruments. Blues can be Memphis-Blues subdivided into several subgenres ranging from country to urban blues that were more or Memphis-Blues less popular during different periods of the 20th century. Memphis-Blues Best known are the Delta, Piedmont, Jump and other blues styles Memphis-Blues. World War II marked the transition from acoustic to Memphis-Blues electric blues and the progressive opening of blues music to a wider audience, especially white listeners. In the 1960s and 1970s, a Memphis-Blues hybrid form called blues-rock evolved.
The basic Memphis-Blues 12-bar lyric framework of a blues composition is reflected by a standard harmonic progression of 12 bars in a 4/4 time signature. The blues chords associated to a Memphis-Blues twelve-bar blues are typically a set of three different chords played over a 12-bar scheme. They are labeled by Roman numbers referring to Memphis-Blues the degrees of the progression. For instance, Memphis-Blues for a blues in the key of C, C is the tonic chord (I) and F is the subdominant Memphis-Blues (IV).