Pitch, the subjective impression of whether individual speech sounds are perceived as relatively high or low, is an important characteristic of spoken language, contributing in some languages to the lexical identity of words and in all languages to the perception of the intonation pattern of utterances. Pitch corresponds to the physiological parameter of the frequency of vibration of the vocal folds, the fundamental frequency, which can be measured in cycles per second or hertz.Estimating and measuring fundamental frequency and modelling pitch is not easy. After presenting some automatic models of pitch, we address issues related to the detection and measurement of fundamental frequency, including tracking/detection errors, and explain how many of these errors can be avoided by the appropriate choice of pitch ceiling and floor settings. We finally discuss the use of acoustic scales (linear, logarithmic, psychoacoustic) for the measurement of pitch. Based on evidence from recent findings in neuroanatomy, neurophysiology, behavioural studies and speech production, we suggest that a new scale, the Octave-Median (OMe) scale, appears to be more natural for the study of speech prosody.