 A straightforward account identifies pitch with periodicity (perhaps within some range). Having pitch is being periodic (see O’Callaghan 2007, ch. 6). Periodicity can be expressed in terms of fundamental frequency, so individual pitches are fundamental frequencies. This has advantages as an account of pitch. It captures the linear ordering of pitches. It also explains the musical intervals, such as the octave, fifth, and fourth, for example, which are pitch relations that hold among periodic tones. Musical intervals correspond to whole-number ratios between fundamental frequencies. Sounds that differ by an octave have fundamental frequencies that stand in 1:2 ratios. Fifths involve a 2:3 relationship, fourths are 3:4, and so on. This also allows us to revise the linear pitch ordering to accommodate the auditory sense in which tones that differ by an octave nonetheless are the same pitch. If the pitch ordering is represented as a helix, upon which successive octave-related tones fall at a common angular position, each full rotation represents doubling frequency.