It would take a lot of CPU horsepower. You would need to sample at about
8K samples per second (about AM radio quality). Analyze the last seconds worth of data 15 times a second, and then determine the rhythm, I would do that with finding the power (sum of selected amplitudes).
What you are trying to do is reasonable but it takes CPU power and a fairly sophisticated algorithm.
Other interesting effects are changing the color of the bullets based on the power at different frequencies. Do a fast fourier transform to get the spectrum, then analyze the power of each frequency, use that to to set the color of the shooting.
Eric