Sound sensore

Hello i want to make a circuit that regonizet low voltage from bluetootth module( or aux) audio output and can can control 12v+ relay or negative maybe better. If i play some sound to have pernamently connect relay maybe with 10-30 second delay until turn off becaus dont want to turn off relay when the sound end and new is play soon. All cicruits i try blink only leds.. can someon help me? I work on automatic switch when someon call me to bluetooth/ aux or if i play music to automatic switch from radio to bluetooth