what is the problem? sounds not playing? any error messages?

hmm, well the below code works on my machine fine.
The mp3s I'm using are all very short, so if yours are very long perhaps there is some sort of buffer size issue, you might try different buffer sizes within the loadFile().
dan
===============
import ddf.minim.*;
Minim minim;
AudioPlayer player[]=new AudioPlayer[4];
String filenames[] = new String[]{"cake_neverThere_F_2.mp3", "missyElliot_workIt_G_1.mp3", "styx_mrRoboto_Eb_2.mp3", "who_iCantExplain_E_2.mp3"};

void setup(){
 minim = new Minim(this);
 for(int i=0;i<4;i++){
   player[i] = minim.loadFile(filenames[i], 2048);
   player[i].play();
 }
}

void draw(){}

void stop(){
for(int i=0;i<4;i++){
   player[i].close();
 }
 minim.stop();
 super.stop();
}