In the old days, MCUs, CPUs, and DACs were extremely expensive, so complex analog/digital hybrid devices used MUXs IC's, like the CD4051 CMOS chip, to get more "bang for your buck" from a single channel DAC chip's output.

Used with an inexpensive MCU, this quad Sample and hold board is an easy and low-cost way to turn a single channel DAC (MCP4921 in this case) into effectively as many DAC output channels as you want.

MUX ICs of course are still used today, but back in the days of classic synths (think mid 1980s to early 2000's) on synthesizers like the Sequential Prophet-5 or Prophet-10, the idea was taken "to the max". This project is a homage to early digital/analog synthesizer design, borrowing many design elements from the Sequential Z80 based Prophet V

The PCB is designed for audio synthesis, but can be used for any application where multiple sample and hold channels are needed--and as long as power is maintained to the circuit, the output of the sampled voltages will not sag over time.

Blog post, with more detail, use cases, and so on, is here: https://audiodiwhy.blogspot.com/2022/03/sequencial-quad-samplehold.html