These are some mini loopers. The difference here is that these use momentary instead of latching switches. The signal is routed through the send return loop only when the switch is down.
The idea for this came up in a discussion about stutter effects. Usually you’d be toggling the pickup selector switch on your guitar but that really only offers a change in volume. What if you wanted to turn a fuzz or distortion on and off quickly and rhythmically? You’d need to tap the switch twice each cycle, which is a little awkward.
The experiment here was to see if a momentary switch made The effects loop musically useful.
These were really easy to make. Just four jacks and the switch. There was was no need for an LED since the effect is only on when your foot is on the button.