Click free unmute using normally open SPST stomp

[nocentelli]

I've got a few tap tempo pedals and a nice carling stomp that all have N.O. SPST switches. I'm trying to achieve a click-free unmute circuit for the delay input to a pt2399 based delay so I can have a "punch in" stomp for King Tubby-style dub action. I know it's easily done with a SPDT and "with tails" buffered bypass (e.g. echobase) but I want to keep the bypass and use a SPST NO switch. So far, i've been using it to simply make and default break the connection between the buffered output and the delay input connection, but leaving the delay input hanging produces some undesirable side effects and artifacts.

I found this (not tried it yet) that claims to do silent AC muting:
http://m.electronicdesign.com/analog/eliminate-clicks-when-muting-single-ended-audio


...but as you can see the momentary action mutes the signal, and I need it to be default mute and momentary unmute. However, the design seems nice and simple and I'm hoping someone can suggest how to use this kind of thing to do momentary unmute.

[Fender3D]

You may use a JFET as in Boss pedals,
If you build half flip-flop you may short to +V the NPN's base to drive the JFET on

BTW
if you have tails, you may use it to drive the input switch (4066, 4053 or whatever) you may invert the switch "logic" with 1 transistor if you're using electronic switches.