I have a simple project for my arduino : light some leds when i send a certain frequency from my smartphone through the jack output . For example , I play a simple audio file generated with a frequency generator (it generates sinwaves, sawtooth, quadrate waves...) at 1kHz --> a red led turns on I play another frequency (5kHz) --> a green led turns on. I read similar questions , but they needed a precise reading of the signal frequency, so they had to convert from AC to DC and from 700mV to 2,5V, is it necessary in my case ? I can also prepare a track with a program called audacity with the current remaining always positive but oscillating between 0 and 0,7 mV. How can i realize my project in the simplest way possible ?