Beat detection algorithm

In case anyone still needs help with this, I've made a simple beat detection API you can use on your GameObject. It's at my Github below:

https://github.com/allanpichardo/Unity-Beat-Detection

@meat5000 MOTHER OF GOD, I've been doing it all wrong! I've been using getOutputData all this time, which from what i understand gives you the db of a certain sample length, what i've been needing to do is change it to getSpectrumData which gives the intensity of a certain sample length, thats why it hasnt been working in loud songs like the one i sent, because it was WAAAAY too loud for it to register anything, but now that it checks for intensity it doesnt even care for the volume.

Still needs some work though, although i can definitely go somewhere from here. ill edit and add the final piece of code once i get it somewhat more accurate, but for now this is a working program: http://pastebin.com/MF63GpGd

Don't know if the thread is dead or what but if anyone here stills wants it here is a slightly changed version of Sgt's script that worked for me, cudos go to SgtPancakes and whoever wrote the article posted by Sgt.

 using UnityEngine;
 using System.Collections;
 
 public class SpectrumDetektor : MonoBehaviour {
     //public AudioClip song;
     public AudioSource song;
     //public GameObject cube;
     private bool Beated;
     private float[] historyBuffer = new float[43];
     private float[] channelRight;
     private float[] channelLeft;
     private int SamplesSize = 1024;
     public float InstantSpec;
     public float AverageSpec;
     public float VarianceSum;
     public float Variance;
     public float Constant;
     
     // Use this for initialization
     void Start () {
         Beated = false;
     }
     
     // Update is called once per frame
     void Update () {
         
         //compute instant sound energy
         //channelRight = song.audio.GetSpectrumData (1024, 1, FFTWindow.BlackmanHarris);  //Normal
         //channelLeft = song.audio.GetSpectrumData (1024, 2, FFTWindow.BlackmanHarris);  //Normal
         //channelRight = song.GetSpectrumData (1024, 1, FFTWindow.Hamming);  //Rafa
         //channelLeft = song.GetSpectrumData (1024, 2, FFTWindow.Hamming);  //Rafa
         
         //InstantSpec = sumStereo (channelLeft, channelRight);  //Normal
         InstantSpec = sumStereo2(song.GetSpectrumData(SamplesSize, 0, FFTWindow.Hamming));  //Rafa
         
         //compute local average sound evergy
         //AverageSpec = sumLocalEnergy ()/historyBuffer.Length; // E being the average local sound energy  //Normal
         AverageSpec = (SamplesSize / historyBuffer.Length) * sumLocalEnergy2(historyBuffer);  //Rafa
         
         //calculate variance
         //VarianceSum = 0;
         //for (int i = 0; i < 43; i++)  //Normal
             //VarianceSum += (historyBuffer[i]-AverageSpec)*(historyBuffer[i]-AverageSpec);
         
         //Variance = VarianceSum/historyBuffer.Length;  //Normal
         Variance = VarianceAdder(historyBuffer) / historyBuffer.Length;  //Rafa
         Constant = (float)((-0.0025714 * Variance) + 1.5142857);  //Normal
         
         float[] shiftingHistoryBuffer = new float[historyBuffer.Length]; // make a new array and copy all the values to it
         
         for (int i = 0; i < (historyBuffer.Length - 1); i++) { // now we shift the array one slot to the right
             shiftingHistoryBuffer[i+1] = historyBuffer[i]; // and fill the empty slot with the new instant sound energy
         }
         
         shiftingHistoryBuffer [0] = InstantSpec;
         
         for (int i = 0; i < historyBuffer.Length; i++) {
             historyBuffer[i] = shiftingHistoryBuffer[i]; //then we return the values to the original array
         }
         
         if (InstantSpec > (Constant * AverageSpec)) { // now we check if we have a beat
             if(!Beated) {
                 Debug.Log("Beat");
                 Beated = true;
             }
         } 
         else {
             if(Beated) {
                 Beated = false;
             }
             Debug.Log("No Beat");
         }
         
         //Debug.Log ("Avg local: " + E);
         //Debug.Log ("Instant: " + e);
         //Debug.Log ("History Buffer: " + historybuffer());
         
         //Debug.Log ("sum Variance: " + sumV);
         //Debug.Log ("Variance: " + V);
         
         //Debug.Log ("Constant: " + constant);
         //Debug.Log ("--------");
     }
     
     float sumStereo(float[] channel1, float[] channel2) {
         float e = 0;
         for (int i = 0; i<channel1.Length; i++) {
             e += ((channel1[i]*channel1[i]) + (channel2[i]*channel2[i]));
         }
         
         return e;
     }
 
     float sumStereo2(float[] Channel) {
         float e = 0;
         for (int i = 0; i < Channel.Length; i++) {
             float ToSquare = Channel[i];
             e += (ToSquare * ToSquare);
         }
         return e;
     }
     
     float sumLocalEnergy() {
         float E = 0;
         
         for (int i = 0; i<historyBuffer.Length; i++) {
             E += historyBuffer[i]*historyBuffer[i];
         }
         
         return E;
     }
 
     float sumLocalEnergy2(float[] Buffer) {
         float E = 0;
         for (int i = 0; i < Buffer.Length; i++) {
             float ToSquare = Buffer[i];
             E += (Buffer[i] * Buffer[i]);
         }
         return E;
     }
 
     float VarianceAdder (float[] Buffer) {
         float VarSum = 0;
         for (int i = 0; i < Buffer.Length; i++) {  //Rafa
             float ToSquare = Buffer[i] - AverageSpec;
             VarSum += (ToSquare * ToSquare);
         }
         return VarSum;
     }
     
     string historybuffer() {
         string s = "";
         for (int i = 0; i<historyBuffer.Length; i++) {
             s += (historyBuffer[i] + ",");
         }
         return s;
     }
 }

This was picking up some beats but not "the beat". I tried with fur elise (piano), which seemed to do the best, picking up the beat here and there and then dropping off again. fatboy slims funk soul brother picked up 1 beat when the song started and that was it, and the doors 'love her madly' picked up 2 beats during the entire song. I can see this working with a simple metronome sound possibly, but as for music, no way.