You can mimic a tone pot @ 10/10 with a 470k or 220k resistor & a 0.022 or 0.047µ cap (the cap is not necessary but it would have a subtle influence on the harmonics).
Solder these components in series then solder the whole between hot and ground.
If you want to fine tune the circuit, replace its resistor with a trim pot and set it by ear.
I've a guitar with such a thing in it, BTW...