Here is a collection of video demos of multiple sound reactive LED circuits I have played with.
First circuit. Uses an Arduino to read data from an electret
microphone and react based on sound level. Sound sensibility is adjusted
with a potentiometer.
The next circuit uses filters, a blue LED that reacts to lower
frequencies, filtered with a low pass circuit, configured with a cutoff
frequency of \~150Hz, while the red one reacts to higher frequencies,
filtered by an high pass circuit, with a cutoff frequency set a little
over 1.5KHz. The sound responsiveness is much better than the previous
The following circuit uses frequency filtering with high power LEDs. The
circuit got a little more complex than the previous one due to power
requirements (different transistors, power source, etc).