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In music, a pulse is an unbroken series of distinct yet identical
periodically occurring short stimuli perceived as points in time (DeLone et. al.
(Eds.), 1975, chap. 3). Ideally, this is opposed to a series of identical but aperiodically occurring stimuli, a series of
periodically occurring yet otherwise differentiated stimuli, or an uninterrupted stream of sound (such as a drone). A pulse may be an unheard event underlining a piece or metric
level, thus the tempo of the piece is how fast the pulse is running, implied by the
performer or listener based on context or past experience, or audible such as in Terry Riley's In C.
Non-ideal pulses varied according to strength or accents, which produce two or three
pulse pulse groups (anything larger being a combination), strong-weak and strong-weak-weak (ibid). In fact,
given an ideal pulse, the most probable reaction for one to have is to perceptually group or differentiate the beats. A pulse
which became to fast would become a drone, a pulse that is to slow becomes isolated
sounds. A pulse that is regularly accented is a meter. An isochronal
or equally spaced pulse on one level that uses varied pulse groups (rather than just one pulse group the whole piece) create a
pulse on the (slower) multiple level that is non-isochronal (a stream
of 2+3... at the eighth note level would create a pulse of a quarter note+dotted quarter note as its multiple level).
Pulse groups may further be distinguished as synchronous, if all pulses on
slower levels coincide with those on faster levels, and nonsynchronous,
if not.
See: beat (music).
Source
- DeLone et. al. (Eds.) (1975). Aspects of Twentieth-Century Music. Englewood Cliffs, New Jersey: Prentice-Hall. ISBN 0130493465.
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