/diy/ - Do It Yourself

Ok I built pic-related on a breadboard to try and combine my TRRS earphone mic signal with a music signal from my phone, but the music signal wasn't audible at all. The circuit has a buffer to reinforce the weak passive mic signal and a summing amplifier to combine the signals at the correct relative amplitudes. R1, R3, and R4 are pots in my circuit, and I noticed that attempting to change the gain by making R3 and R1 different also had no effect. Changing the 500k pot also did nothing. Should I be doing this to the bottom ring (ground) and not the sleeve (mic signal or whatever)?