With this modification for the MF-104Z Analog Delay you can bypass the delay without killing existing echoes. Includes a switch for enabling and disabling Spillover Mode.
Imagine playing an echo-filled chorus, then switching back to playing a dry sound for the verse, all while your echoes naturally decay or create infinitely repeating echo soundscapes then solo over them with echo-free.
That would be cool if the switch was mounted at the bottom where it could be foot activated. Can this be field modified?
That’s awesome! I think all delays should have this
Is the mod also available for the 104SD???
Another suggestion is alternate access to the function via a jack that would accept a footswitch.
That is an interesting thing there! 
it is possible to do this with a momentary stomp switch or a jack but it would take more electronics and be rather more expensive. The switch that is used has multiple poles (means it switches more than one thing at a time) so a simple old fashioned switch is the easiest and least-expensive way to do this (requires no ICs or active electronics, as your other suggestions would).
Cheers,
Amos
Nice, I’m thrilled I wasn’t told about this 
it’s been really busy back in the Moog Lab… actually not many people at Moog knew about this mod, it’s something I cooked up in my spare time a few months ago and happened to mention to Marketing one day… the rest as they say is history. 
Feel free to bring your 104 in for modding any time.
Great idea! Any plans in the future to make this mod a permanent fixture to the 104z?
Definately.
I’d want a 2nd foot switch though.. there’s room for it.
this is great!! How much is it? edit: just saw it one the website…dang, kinda expensive! Still I’ve been wishing that the analog delay had this for ages…guess it’s time to send her in… 
Hey Amos! Im very interested in mod that would do this: A voltage control over delay out via Mix CV,so you can control just delay(wet) output/level.
I use my MF-104Z with line selector-2 channels(one dry,other just delay), so
I can have truebypass. And I can put a LPF and volume pedal or distortion on second ch-before delay,so the signal that comes in is effected,but I cant have
a preset on my Mp-201 for delay level.I know that I could accomplish this with simple VCA,but that is another thing on pedalboard. I need space for more toys!
Another mode I was thinking about is a switch on RM for internal/external
Carrier,so you wont need to plug/unplug the cable for carrier in.
This modes are super useful for guitarist that dont have free hands to do it or they need space and money for other things.
Think about it
i want to know the answer to this too… hint hint
Hrrrmmmm.
I would like to have this option on mine, but I am not sure I want to spend $70 bucks on it.
I wonder if can manipulate the delay time of the spillover with an expression pedal?
Can the spillover be sent through the Moog’s effects loop? If so, your echos can have some movement to them if using modulation/whatever. That would be a huge selling point to me.
Now when you switch it back on, does the delay stop or can you continue adding to the “loop” of delay feedback?
I’ve never played a delay that had a spillover option that would allow you to keep adding to the loop of delay feedback. I am not a tech person, but I don’t think that can be done internally. I would think you would need something like a two amp setup and an amp switcher to achieve that kind of control
FYI – For those curious about the questions I was raising, I received this email from Moog’s Tech Support:
Maybe a worded that wrong, but you know when you crank up the feedback and just play a “C”, the C keeps repeating on and on. Then play a “G” and the “C” doesn’t just vanish they kinda get blurred together a little until the G takes over. I guess that’s the best way I can desribe it. I know it won’t function like an actual looper were you can just keep overdubbing
I get what you are saying. I don’t know if this is the case with the Moog or not, but in my experience with spillovers, when you reactive the bypass switch, the old content disappears. It’s almost like a reset button.
Moog Tech gave me a quick response, you should email (through the form on this site) and clear this up.