it’s a bit old and i don’t have a note, but i can try to explain some simple mod
to replace the clock resistance, turn on the toy and pass your finger (slightly damp) on the resistance, when it changes the tone of the sound it is the right resistance to remove and replaced by a pot (tried several values, but at least 1M I think works well), I think that sometimes I connect the pin 1 of the pot to the ground to have a very low down (with a small trim pot or resistor to adjust the breaking time)
I removed the trigger from the megaphone and soldered the wires so that it works continuously
there is a position with the switches or the sound will pass through the toy without FX, a kind of byepass (marked NO FX on my box : C and D )
I left the toy switches on the circuit (too boring to unsolder) and made an extension with wires to new switches.
put a jack socket instead of the mic (add an input pot would surely be good)
a output jack socket instead of the speaker, with a resistor of the same value of the speaker (8 or 4 ohm) to tip to ground (the left jack on the photo below)
and add a volume pot for the output
for LFO , a little circuit with 555 like this (maybe not exactly the same ?)
or this (add a resistor for the led, and a pot instead the trimmer)
with 2 led : one for the indicator led , and another for the vactrol (connected to the pin of the pitch pot
an attenator pot on the vactrol led for LFO mix i think
a switch for on/off LFO circuit power
for the feedback i don’t remember, but i put some schem which I must have been inspired
I also found this in my files for WET / DRY I did not make this mod, but it can help, i remember that it’s not for the same toy but …
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if there are other questions don’t hesitate 
2 others i’ve made (not with the same toy)
a very cheap one (with only 3 positions)
and my fisrt (inspired by Simon the Magpie!) with a real byepass switch, a body contact and a pot action very strange
here’s with a glitch toy, at 0.45’
