public final class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root, 300, 275));
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }

}

@Mod(modid = Radio.MOD_ID, name = Radio.MOD_NAME, version = Radio.MOD_VERSION)
public class Radio {

    public static final String
            MOD_ID = "radio",
            MOD_NAME = "Radio",
            MOD_VERSION = "1.0";

    private final static KeyBinding playButton = new KeyBinding("key.playButton", Keyboard.KEY_NUMPAD5, "key.categories.radio");
    private final static KeyBinding stopButton = new KeyBinding("key.stopButton", Keyboard.KEY_NUMPAD4, "key.categories.radio");

    private MediaPlayerFX player;
    private static Logger logger;

    @Mod.EventHandler
    public void preInit(FMLPreInitializationEvent event) {

        logger = event.getModLog();

        if (event.getSide().isClient()) {
            ClientRegistry.registerKeyBinding(playButton);
            ClientRegistry.registerKeyBinding(stopButton);
            FMLCommonHandler.instance().bus().register(this);
            this.player = new MediaPlayerFX();
        }

    }

    @SubscribeEvent
    @SideOnly(Side.CLIENT)
    public void key(InputEvent.KeyInputEvent event) {

        if (playButton.isPressed()) {
            this.player.play();
        }

        if (stopButton.isPressed()) {
            this.player.stopped();
        }

    }

    private static class MediaPlayerFX extends Application {

        private MediaPlayer player;

        @Override
        public void start(Stage stage) throws Exception {
            this.player = new MediaPlayer(new Media("mp3 link"));

            this.player.setOnReady(() -> {
                logger.info("onReady");
            });

            this.player.setOnError(() -> {
                logger.info("onError");
            });

            this.player.setOnStopped(() -> {
                logger.info("onStopped");
            });

            this.player.setOnEndOfMedia(() -> {
                logger.info("onEndOfMedia");
                this.player.stop();
            });

            this.player.setOnPaused(() -> {
                logger.info("onPause");
            });

        }

        public static void main(String[] args) {
            launch(args);
        }

        private void play() {
            this.player.play();
        }

        private void stopped() {
            this.player.stop();
        }

    }

}