Thread is not working

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.IO;

namespace BackGroundMusicGP
{
    class BkGrndMusic
    {
      private string _command;
     private bool isOpen;
  [DllImport("winmm.dll")]

  private static extern long mciSendString(string strCommand,StringBuilder strReturn,int iReturnLength, IntPtr hwndCallback);

  public void Close()
  {
     _command = "close MediaFile";
     mciSendString(_command, null, 0, IntPtr.Zero);
     isOpen = false;
  }

  public void Open(string sFileName)
  {
     _command = "open \"" + sFileName + "\" type mpegvideo alias MediaFile";
     mciSendString(_command, null, 0, IntPtr.Zero);
     isOpen = true;
  }

  public void Play(bool loop)
  {
     if(isOpen)
     {
        _command = "play MediaFile";
        if (loop)
         _command += " REPEAT";
        mciSendString(_command, null, 0, IntPtr.Zero);
     }
      }
  public void playMusic()
  {
      string path = "E:\\abc\\Habib.mp3";
       string filename = Path.GetFileName(path);
      Open(filename);
      Play(false);
  }
    }
}

public partial class Form1 : Form
   {
       BkGrndMusic objBkMusic;
       int i = 0;
       public Form1()
       {
           InitializeComponent();
           objBkMusic = new BkGrndMusic();
       }
       private void button1_Click(object sender, EventArgs e)
        {
           Thread t = new Thread(new ThreadStart(objBkMusic.playMusic));
            t.Start();  // it doesn't work
           //objBkMusic.playMusic(); // it works
         }