modulations

Modulations refer to processes that transform a signal or musical material by varying a parameter over time. In communications and signal processing, modulation means altering a property of a carrier signal—such as its amplitude, frequency, or phase—in proportion to a modulating signal in order to encode information for transmission and later retrieval. In music, modulation is the change of tonal center or key within a piece, typically to provide variety, contrast, or a sense of progression.

In analog telecommunications, common modulation schemes include amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). In digital communications, modulation maps data to discrete signal states, as in amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM). Modulation affects bandwidth, power efficiency, and resilience to noise. Demodulation at the receiver reverses the process to recover the original data. Carrier and baseband concepts, synchronization, and channel conditions influence performance and choice of scheme.

In music theory, modulation denotes a shift from one key to another. Common techniques include pivot-chord modulation, direct or abrupt modulation, and chromatic or enharmonic modulation. Modulation is used to heighten contrast, create tension, or prepare a cadence, and it can establish related or distant keys depending on the composer’s intent.