def sound1():
    path = r'C:/sound'
    for sound in os.listdir(path):
        playsound('%s/%s' % (path, sound))

def quit():
    root1.quit()

def wind():
    global root1
    root1 = Tk()
    btn1 = Button(text="Запустить проигрыватель", command=sound1)
    btn2 = Button(text="Выйти", command=quit)
    btn1.pack()
    btn2.pack()
    root1.mainloop()
t = threading.Thread(target=wind).start()
j = threading.Thread(target=sound1).start()