You can use the following function to determine whether the current CD inside the CD-ROM drive is an Audio CD.

function IsAudioCD(CDDrive : Char) : boolean;

var
  VolumeName, DrivePath : string;
  MaximumComponentLength, FileSystemFlags : DWORD;

begin
  DrivePath := CDDrive + ':\';
  Result := FALSE;

  if (GetDriveType(PChar(DrivePath)) = DRIVE_CDROM) then
    begin
      SetLength(VolumeName, 64);
      GetVolumeInformation(PChar(DrivePath), PChar(VolumeName), Length(VolumeName), nil, MaximumComponentLength,
                                          FileSystemFlags, nil, 0);

      if (lStrCmp(PChar(VolumeName),'Audio CD') = 0) then Result := TRUE;
    end;
end;

The function returns a value of TRUE if it's a Audio CD or FALSE, otherwise.

For Example:
-----------------

if IsAudioCD('D') then
  ShowMessage('There is a Audio CD in the CD-ROM drive');

This example assume that the "D" drive is a CD-ROM drive, and will display a message if it's an Audio CD.