I don't know what is the level of knowledge programming microcontrollers that you have. But if you have a microcontroller with ADC, you don't need to put external filters to separate low frecuencies from middle frecuencies and high frecuencies. All can be donde by software in the microcontroller.
Some ideas how to do:
Supposse, you sample at 8khz, and output leds using PWM signals (most of microcontrollers have ADC and more than 1 PWM)
You can measure the RMS value of signal just adding a fixed number of samples.
You can measure the "frecuency", just counting the zero crossings of signal.
Or, you can implement digital Z filters, all by soft to obtain the RMS value acording of spectrum of signal.
Hope it helps.