Android : Lost Equalizer control when play next song

Question

I have successfully applied Audio effect to MediaPlayer using a singleton Equalizer but when play other songs Audio effect is not applied anymore although I can still use that singleton Equalizer to setBandLevel(), usePreset() and hasControl() method still returns true.

Here is how I user Equalizer and MediaPlayer

MediaPlayer mPlayer = new MediaPlayer();
Log.e(TAG, "audio session id = " + mPlayer.getAudioSessionId());
if(mAudioSessionId == 0) //play first song
    mAudioSessionId = mPlayer.getAudioSessionId();
else
    mPlayer.setAudioSessionId(mAudioSessionId); //use old audio session id for next song

......

Can you please tell me why I lost equalizer control although I already set the same audio session id for new MediaPlayer instance? Thank you.