face detection & background music simultaneously

I wanna play background music and face detection simultaneously. But i couldn't play the music, though the playMusic() function works fine individually(in a separate project). When i call the function inside the face detection system then no music heard. i can't find out where the problems are.

Environment:
Luxand FaceSDK 3.0
C#.NET Framework 3.5

The Following Programs (Play Background Music) Works Fine
// CLASS: BackGroundMusicGP


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\\ss.mp3";
string filename = Path.GetFileName(path);
Open(filename);
Play(false);
}
}
}

///////////////////////////

public partial class Form1 : Form
{
BkGrndMusic objBkMusic;

public Form1()
{
InitializeComponent();
objBkMusic = new BkGrndMusic();
}
private void button1_Click(object sender, EventArgs e)

{
    objBkMusic.playMusic(); // it works
}

But the following code doesn't play the music when i call objBkMusic.playMusic();  inside the face detection system. For clarification, here is a portion of the program(FaceSDK) is given.

public void showCamera(PictureBox picBox)
        {
                        
            while (!needClose)
            {
                
                Int32 imageHandle = 0;
                if (FSDK.FSDKE_OK != FSDKCam.GrabFrame(cameraHandle, ref imageHandle)) // grab the current frame from the camera
                {
                    Application.DoEvents();
                    continue;
                }

                IntPtr hbitmapHandle = IntPtr.Zero; // to store the HBITMAP handle
                FSDK.SaveImageToHBitmap(imageHandle, ref hbitmapHandle);
                Image frameImage = Image.FromHbitmap(hbitmapHandle);
                Graphics gr = Graphics.FromImage(frameImage);
                
                string[] strResult = new string[2];

                Pen xPen = new Pen(Color.Red, 5);
                // if a face is detected, we can recognize it
                if (FSDK.FSDKE_OK == FSDK.DetectFace(imageHandle, ref facePosition))
                {
                                        
                    gr.DrawRectangle(xPen, facePosition.xc - facePosition.w / 2, facePosition.yc - facePosition.w / 2, facePosition.w, facePosition.w);
                    //gr.DrawEllipse(xPen, facePosition.xc - facePosition.w / 2, facePosition.yc - facePosition.w / 2, facePosition.w, facePosition.w);
                    
                    // create a new face template
                    byte[] template = new byte[FSDK.TemplateSize];
                    FSDK.GetFaceTemplateInRegion(imageHandle, ref facePosition, out template);

                    strResult = MatchTemplateWithDatabase(template);
                    // if face matches with database's face data
                    if (!strResult[0].Equals(""))
                    {
                            xVoice = new SpeechSynthesizer();
                            xVoice.Speak("Hello " + strResult[1]); //speak by name
                            xVoice.Dispose();
                    }

                }
                else  // if there is no face in the screen, then background music will be played
                {
                        objBkMusic.playMusic();   // doesn't work

                 }

                picBox.Image = frameImage;
                FSDK.FreeImage(imageHandle); // delete the FSDK image handle
                DeleteObject(hbitmapHandle); // delete the HBITMAP object
                GC.Collect(); // collect the garbage after the deletion
                // make UI controls accessible
                Application.DoEvents();
            }
        
            FSDKCam.CloseVideoCamera(cameraHandle);
            FSDKCam.FinalizeCapturing();

        }

///////////////////////

My problem is here

         if  (FSDK.FSDKE_OK == FSDK.DetectFace(imageHandle, ref facePosition))
                {
                       //
                       //
                }
        else  // if there is no face in the screen, then background music will be played
                {
                        objBkMusic.playMusic();   // doesn't work

                 }