circuit to smooth audio voltage jump?

[boneless]

Hi All,

I recently saw this on Sonicstate

https://www.tindie.com/products/midierror/super-smash-button-arcade-audio-gate/

When I listened to the youtube I couldn't hear audio pops, so I assumed he'd put in a circuit to tame the voltage jump, but it turns out he hadn't. It's literally a momentary switch wired to the jacks.

In tha past I DIY'd a bank of these for CV, but gave up using it for audio coz of POP's, at the beginning and end of the button press. Which got me thinking, what circuit could I use to sort of 'slew' the voltage jumps so I get zero voltage crossings, and no pops.

Thanks in advance synth heads!