Have just been playing with it a bit, and have got a better grasp of how these things talk to eachother. Will go away and read about the getspectrumanalyser() and see where to go from there.
What I was meaning is that if it is a low frequency, the rmp3 will return a value to the arduino that will activate one output, and if it is a mid range frequency, the rmp3 will return another value to the arduino to trigger a different output.
With the aim of having a different output for a different frequency range.
Thanks