Playing small motors from synth and arduino

[van_der_decken]

@hk_jh

Is adding series resistor of 10k or so between the tip of the jack to the arduino analog pin will solve that?

No, it will not. If you've already applied voltages outside of 0-5V to A0, you have already damaged it. The longer you continue to do so, the more you will damage it. Eventually it will quit working.