Varying pitch

Pitches may be described in various ways, including high or low, as discrete or indiscrete, pitch that changes with time (chirping) and the manner in which this change with time occurs: gliding; portamento; or vibrato, and as determinate or indeterminate. Musically the frequency of specific pitches is not as important as their relationships to other frequencies — the difference between two pitches can be expressed by a ratio or measured in cents. People with a sense of these relationships are said to have relative pitch while people who have a sense of the actual frequencies independent of other pitches are said to have "absolute pitch", or "perfect pitch".