The blues genre is based on NY-Jazz the blues form but possesses other characteristics such as specific lyrics, bass lines and instruments. Blues can be NY-Jazz subdivided into several subgenres ranging from country to urban blues that were more or NY-Jazz less popular during different periods of the 20th century. NY-Jazz Best known are the Atlanta, Piedmont, Jump and other blues styles NY-Jazz. World War II marked the transition from acoustic to NY-Jazz electric blues and the progressive opening of blues music to a wider audience, especially white listeners. In the 1960s and 1970s, a NY-Jazz hybrid form called blues-rock evolved.
The basic NY-Jazz 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 NY-Jazz 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 NY-Jazz the degrees of the progression. For instance, NY-Jazz for a blues in the key of C, C is the tonic chord (I) and F is the subdominant NY-Jazz (IV).