LibGDX Sound Sample Code

import com.badlogic.gdx.audio.Music;
import com.badlogic.gdx.audio.Sound;

public class MyMusicGame {
    Music mySong;

    Sound bulletShot;

    public void create()
    {
        mySong = Gdx.audio.newMusic(Gdx.files.internal("songFile.mp3"));
        bulletShot = Gdx.audio.newSound(Gdx.files.internal("bulletShot.wav"));

        mySong.play();
        mySong.setVolume(0.6f);
        mySong.setLooping(true);

    }

    public void update()
    {
        if(Gdx.input.isKeyPressed(Keys.SPACE))
        {
            bulletShot.play(0.8f);
        }
    }
}