In the 13th century, the fourth and fifth together were the "concordantiae mediae" (middle consonances) after the unison and octave, and before the thirds and sixths. The fourth came in the 15th century to be regarded as dissonant on its own, and was first classed as a dissonance by Johannes Tinctoris in his "Terminorum musicae diffinitorium" (1473). In practice, however, it continued to be used as a consonance when supported by the interval of a third or fifth in a lower voice.