<P> Chords may be also represented by a few different notation systems such as sheet music and electronic music . A basic example of the progression would look like this, using T to indicate the tonic, S for the subdominant, and D for the dominant, and representing one chord . In Roman numeral analysis the tonic is called the I, the sub-dominant the IV, and the dominant the V. (These three chords are the basis of thousands of pop songs, which thus often have a blues sound even without using the classical twelve - bar form .) </P> <P> Using said notations, the chord progression outlined above can be represented as follows . </P> <Table> <Tr> <Td> <Dl> <Dd> <Table> Functional notation: <Tr> <Td> T </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> </Table> </Dd> </Dl> </Td> <Td> <Table> Roman - numeral notation: <Tr> <Td> I </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> IV </Td> <Td> IV </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> V </Td> <Td> V </Td> <Td> </Td> <Td> </Td> </Tr> </Table> </Td> </Tr> </Table> <Tr> <Td> <Dl> <Dd> <Table> Functional notation: <Tr> <Td> T </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> </Table> </Dd> </Dl> </Td> <Td> <Table> Roman - numeral notation: <Tr> <Td> I </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> IV </Td> <Td> IV </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> V </Td> <Td> V </Td> <Td> </Td> <Td> </Td> </Tr> </Table> </Td> </Tr>

The 12-bar blues has three verses in what pattern