The existence of the blue note within music derives, in part, from the fact that equal temperament in western diatonic harmony is an artifice or compromise originally employed in the eighteenth century to address problems posed in the creation of keyboard instruments. Equal temperament was an artificial ‘straightening out’ of a tendency for the natural harmonic series (musical intervals as they exist in nature) to go off at a tangent, meaning that higher intervals and octaves in their natural form are of a different pitch than the lower intervals and octaves. This made it difficult to create keyboard instruments that were ‘coherent’. Hence, the blue note attempts to correct this artifice by playing a note that is closer to the interval as it exists in the natural harmonic series. Country blues, in particular, features wide variations from the diatonic pitches with emotive blue notes.