For real, the idea of using a shift register to “strum” a guiro can be applied to simulate other traditional instruments with a “strum-like” pattern.
The implementation seems simple enough that even i can probably get a hacky thing goin. You just need an astable 555 circuit and a serial to parallel shift register. The clock is what slows the strum, and i imagine if you wanted to shift the emphasis of the strum speed over time, you could use CV to affect the clock of the 555 with like an envelope or something. That way you can have a strum that is not uniform, and has a faster beginning or end.
I imagine the triggers can go to something like the Kosmo #453 Preset found in the below video, which uses very similar code to the baby 8 sequencer. You’d basically use the buttons on the neck of the guitar to trigger the presets instead of on/off switches. Then, the presets would be used to tune in the voltages for frequencies routed to VCOs!