Metronome in the context of "Conductor (music)"

A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. Winding the timepiece, by turning a knob or key, stores energy in the mainspring by twisting the spiral tighter. The force of the mainspring then turns the clock's wheels as it unwinds, until the next winding is needed. The adjectives wind-up and spring-powered refer to mechanisms powered by mainsprings, which also include kitchen timers, metronomes, music boxes, wind-up toys and clockwork radios.

Mainsprings appeared in the first spring-powered clocks, in 15th-century Europe. The mainspring replaced the weight hanging from a cord wrapped around a pulley, which was the power source used in all previous mechanical clocks.

In musical terminology, tempo (Italian for 'time'; plural 'tempos', or tempi from the Italian plural), measured in beats per minute, is the speed or pace of a given composition, and is often also an indication of the composition's character or atmosphere. In classical music, tempo is typically indicated with an instruction at the start of a piece (often using conventional Italian terms) and, if a specific metrical pace is desired, is usually measured in beats per minute (bpm or BPM). In modern classical compositions, a "metronome mark" in beats per minute, indicating only measured speed and not any form of expression, may supplement or replace the normal tempo marking, while in modern genres like electronic dance music, tempo will typically simply be stated in bpm.

Tempo (the underlying pulse of the music) is one of the three factors that give a piece of music its texture. The others are meter, which is indicated by a time signature, and articulation, which determines how each note is sounded and how notes are grouped into larger units. While the ability to hold a steady tempo is a vital skill for a musical performer, tempo is malleable. Depending on the genre of a piece of music and the performers' interpretation, a piece may be played with slight variations in tempo, known as tempo rubato, or significant variations. In ensembles, the tempo is often maintained by having players synchronise with a conductor or with a specific instrumentalist, for instance the first violin or the drummer.

In electronics and especially synchronous digital circuits, a clock signal (historically also known as logic beat) is an electronic logic signal (voltage or current) which oscillates between a high and a low state at a constant frequency and is used like a metronome to synchronize actions of digital circuits. In a synchronous logic circuit, the most common type of digital circuit, the clock signal is applied to all storage devices, flip-flops and latches, and causes them all to change state simultaneously, preventing race conditions.

A clock signal is produced by an electronic oscillator called a clock generator. The most common clock signal is in the form of a square wave with a 50% duty cycle. Circuits using the clock signal for synchronization may become active at either the rising edge, falling edge, or, in the case of double data rate, both in the rising and in the falling edges of the clock cycle.