A circuit on an analog synthesizer that, when triggered (usually by a clock pulse), looks at (samples) the voltage at its input and then passes this voltage on to its output unchanged, regardless of what the input voltage does in the meantime (the hold period), until the next trigger is received. In one familiar application, the input was a noise source and the output was connected to oscillator pitch, which caused the pitch to change in a random staircase pattern. The sample-and-hold effect is often emulated by digital synthesizers through an LFO waveshape called "random."