<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (August 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (August 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> The twelve - bar blues or blues changes is one of the most prominent chord progressions in popular music . The blues progression has a distinctive form in lyrics, phrase, chord structure, and duration . In its basic form, it is predominantly based on the I, IV, and V chords of a key . </P> <P> The blues can be played in any key . Mastery of the blues and rhythm changes are "critical elements for building a jazz repertoire". </P>

The twelve-bar blues and the aaba are examples of