An “analog shift register” (ASR) is a module that receives and stores a series of voltage values and then sequentially outputs these values at a specified rate, typically triggered by an external clock signal. The module is named after the digital shift register concept, which performs a similar function in digital systems but with digital values (binary) rather than analog voltages.
An analog shift register can be used to create evolving sequences, polyphonic effects, and complex modulation patterns in a modular synthesizer setup. When an incoming voltage value is received by the ASR, the current values stored in the module are shifted along a chain of storage stages, and the oldest value is output and replaced by the new value. The number of storage stages varies depending on the design of the ASR module, with each stage outputting its stored voltage value simultaneously.
Here’s an example of how an ASR might be used in a modular synthesizer patch:
- A control voltage (CV) from a sequencer or other voltage source is fed into the ASR’s input.
- The ASR is triggered by a clock signal, which determines the rate at which the stored voltages are shifted through the storage stages.
- The output voltages from the ASR’s stages are used to control various parameters of other modules in the synthesizer, such as the pitch of oscillators, filter cutoff frequencies, or modulation depths.
By connecting the outputs of an analog shift register to different modules in a modular synthesizer, a musician can create evolving and organic patterns that change over time. The ASR is particularly useful in generative and experimental patches, as it can introduce an element of unpredictability and complexity to the sound.