player.h:

#ifndef PLAYER_H
#define PLAYER_H

#include <phonon/MediaObject>
#include <phonon/SeekSlider>
#include <phonon/MediaSource>
#include <phonon/AudioOutput>
#include <Phonon/VolumeSlider>
#include <QFile>
#include "mainwindow.h"

class Player : public MainWindow
{
    Q_OBJECT

public:
    Player();
    Phonon::MediaObject *player;
    Phonon::AudioOutput *device;
    Phonon::SeekSlider *seekSlider;
    Phonon::VolumeSlider *volumeSlider;
    QFile *song;
    QStringList queue;

    void play();
    void stop();
    void pause();
    void setSong(QString songPath);

public slots:
    void handleTick(qint64 n);
    void aboutToFinish();
};

#endif // PLAYER_H

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTableWidget>
#include "song.h"

class Player;

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);

    Player *player;

    QTableWidget *songList;
    QTableWidgetItem *title;
    QTableWidgetItem *artist;
    QTableWidgetItem *size;
    QTableWidgetItem *fileName;
    QTableWidgetItem *length;

    void playSong();
    void initTable();
    void addToList(QString t, QString a, QString l, QString s, QString f);
    void removeFromList(int row);

    ~MainWindow();
private:
    Ui::MainWindow *ui;

};

#endif // MAINWINDOW_H