2 LM386 amplifiers to 1 speaker

I haven't seen a piezo mic since about 1962. It is completely different to an electret mic. The resistor R4 that powers an electret mic is not used with a piezo mic. The electret mic has a Jfet impedance converter inside for its fairly low output impedance but a piezo mic has a very high output impedance that might need a preamp with a very high input impedance.
A piezo mic might have many strong high frequency resonances.

Guru, this is a guitar pickup i made by embedding a piezo disc into the bridge of the guitar. I would like to mix that with a media player through 1 speaker. Let's step back to my original schematic with a couple new resistors added:
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How does that look?

Thanks for all your time and help, once again!

The high input impedance of a Jfet preamp is used with a magnetic and a piezo guitar pickup.

I trhink you should reverse the volume controls so that the slider connects to the 10k resistor. Then the tiny 47nf capacitor feeding into the 25k pot (that does not change its resistance) cuts low frequencies below 127Hz instead of cutting all low frequencies if you wire it like your schematic.

Thanks Guru! Is this what you mean? What should I change the .47n cap to?

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Thanks for all your help,
-Scott

The lowest frequency of an ordinary guitar is low E at 82.4Hz. If the reactance of a coupling capacitor is equal to the total of its source and load resistances then its level is down 0.707 times which is -3db. The total of the source and load resistances are about 26k ohms so the capacitor value needs to be about (1 divided by 2 x pi x R x C) 150nF so that 84.2Hz is reduced less than -3dB. Use 220nF if you can't find 150nF.