....
 Thread eventMusic = new Thread(new EventMusic());
... check different conditions ... (every 0.02s)
 if everything is ok  -> eventMusic.run();

package Shooter2Dv23082013;
import javazoom.jl.decoder.JavaLayerException;
import javazoom.jl.player.Player;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class EventMusic implements Runnable{
    @Override
    public void run() {

        try {
            Player p = new Player(new FileInputStream(getClass().getClassLoader().getResource("res/nameSong.mp3").getPath()));
            p.play();
        } catch (JavaLayerException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();}


    }
}

package Shooter2Dv23082013;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Random;
import javazoom.jl.decoder.JavaLayerException;
import javazoom.jl.player.Player;

public class EventMusic implements Runnable{
    private int countCollisions;
        @Override
        public void run() {
            String path=null;
            switch (this.countCollisions){
                case 1: path="res/firstblood.mp3"; break;
                case 2: path="res/megakill.mp3"; break;
                case 3: path="res/tripplekill.mp3"; break;
                case 4: path="res/ultrakill.mp3"; break;
                case 10: path="res/ownage.mp3"; break;
                case 20: path="res/unstoppable.mp3"; break;
                case 30: path="res/godlike.mp3"; break;
                case 40: path="res/holyshit.mp3"; break;
                    default:
                        Random rand = new Random();
                        int value = rand.nextInt(3)+1;
                        if (value==1){ path="res/defaultkill1.mp3"; break;}
                        if (value==2){ path="res/defaultkill2.mp3"; break;}
                        else { path="res/defaultkill3.mp3"; break;}
            }
            try {
                Player p = new Player(new FileInputStream(getClass().getClassLoader().getResource(path).getPath()));
                p.play();
                p.close();
            } catch (JavaLayerException e) {
                e.printStackTrace();
            } catch (FileNotFoundException e) {
                e.printStackTrace();}
        }
    public EventMusic(Integer countCollisions){
        this.countCollisions=countCollisions;
    }
 }