Hi there!
I ask myself if anyone knows a way to get specific information about the peaks of each of the (or parts of the) frequencies in a current playback.
I hope you can understand me… :roll:
What I want to achieve in my game is the following:
At the end there shall be a terrain which functions like a big, threedimensional visualizer of the music that is played. So, let's say the deep frequencies are in the north of the terrain, the high ones in the south. Every time a bassdrum is kicked f.e. there errupts a big mountain in the north. 
So what I need to do is to grab the data I need. But I have no clue how to do that… :?
I don't really know how to get that info, but I know it's possible to use Fourier transform to separate complex signals into multiple harmonic sines and cosines that make up that signal. Then it's possible to teach a neural network f.e. which note is played.
But as I see you need just frequencies. I would start off by making a program that makes a graph of audio signal. Then I would figure out how to get the frequencies from that data. I think getting the bass drum would be the hardest part and would require maths and neural networks.
Anyways if you make some progress, please let me know also
One more thing. I once asked from this forum about something similar and blue_week replied:
i used http://code.compartmental.net/tools/minim/ to make a guitar tuner once…
it's designed for processing, but can just as easily be used with jME.
Hey many thanks!
I didn't thought of an FFT, but that's the solution, of course!
Thanks for the link, also. That Minim is a library I could use in many different ways (not just for JME but for several java-projects). The nicest part is that it comes along with an FFT and a manual which includes getting the values of frequency bands! 
http://code.compartmental.net/tools/minim/manual-fft/
Thanks, man!
Okay, I’ll use this to showcase some code and an early screenshot, okay? Still poor graphics, but:
The code was pretty simple. Just generate a TerrainBlock (I used a modified version, because my slow PC couldn’t handle the VBOInfo with more than 10fps) and go over the heightMap.
In the update-Method call something like this:
private void processMusic() {
boolean beatHit = false;
if (beat.isKick() || beat.isSnare())
beatHit = true;
if (beatHit) {
beatCounter = 0;
sData = mPlayer.getFreqBands();
workingHeightMap = sData.getBands();
for (int i = 0; i < 484;/*sData.getSpecSize();*/ i++) {
workingHeightMap[i] = FastMath.clamp(workingHeightMap[i], 0, 2.55f);
workingHeightMap[i] = workingHeightMap[i] / 12;
}
}
float beatTime = 100;
if (heightMap != null && workingHeightMap != null && beatCounter < beatTime) {
for (int i = 0; i < heightMap.length; i++) {
float[] theBigger;
float[] theSmaller;
if (heightMap[i] >= workingHeightMap[i]) {
theBigger = heightMap;
theSmaller = workingHeightMap;
} else {
theBigger = workingHeightMap;
theSmaller = heightMap;
}
float distance = theBigger[i] - theSmaller[i];
float perc = 100 * (beatCounter / beatTime);
float newVal = distance * (perc / 100) - theSmaller[i];
if (heightMap[i] < workingHeightMap[i])
heightMap[i] += newVal;
else
heightMap[i] -= newVal;
}
//go over the heightMap to make a square be zero where the chessfield is
for (int x = 8; x < 14; x++)
for (int y = 12; y < 19; y++)
heightMap[x + (y * 22)] = 0;
tb.setHeightMap(heightMap);
tb.update();
} else if (beatCounter >= beatTime)
beatCounter = 0;
beatCounter++;
}
The tb.update method is the same as the updateFromHeightMap method in the original TerrainBlock class. As you see, did I link the whole thing to Minim's BeatDetector, which allows pretty cool results.
sData is of type StreamData which simply is a Dataholder class for storaging the fft-Data, the number of bands which are used (which is the totalSize of the heightMap) and the mp3's MetaData.
The getFrequency method looks like this:
public StreamData getFreqBands() {
if (player.isPlaying()) {
fft.forward(player.mix);
float[] bands = new float[fft.specSize()];
for(int i = 0; i < fft.specSize(); i++)
{
float freq = fft.getBand(i);
bands[i] = freq;
}
return new StreamData(fft.specSize(), bands, player.getMetaData());
}
wow, cool