Merge / join WAV files Delphi [duplicate]

This question already has an answer here:

• create a wav file from multiple wav files in delphi 1 answer

I want to join several WAV files in Delphi Xe6. I use this code, but it isn't always working, and doesn't recognize the data chunk if it's position is not 44 bytes. If the file contains metadata at the first part of the file, the result will corrupted. If there is a metadata at the end of the WAV, you hear a cracking after the content.

Do you have any idea? Using DirectX, using a more sophisticated procedure?

Thank you.

The code is:

unit concatwav;

interface

uses
 Classes,sysutils;

type
 TConcatWave = class(TThread)
 private
 { Private declarations }
 FileList: TStrings;
 FileStream:TFileStream;
 protected
 procedure Execute; override;
 public
constructor createwithlist(wavname:string; suspended:boolean;aFileList: TStrings);
destructor destroy;override;
procedure JoinWavesToFile;
 end;

implementation
constructor TConcatWave.createwithlist(wavname:string; suspended:boolean;aFileList: TStrings);
begin
inherited create(true);
freeonterminate:=true;
FileList:=TStringList.Create;
FileList.Text:= aFileList.Text;
FileStream:=TFileStream.Create(wavname,fmCreate);
if not suspended then resume;
end;

destructor TConcatWave.destroy;
begin
FileList.Free;
FileStream.Free;
inherited destroy;
end;

procedure TConcatWave.JoinWavesToFile;
var
 I: Integer;
 FileSize: LongInt;
 InStream: TFileStream;
begin
 for I := 0 to FileList.Count -1 do
 if FileExists(FileList[I]) then
 begin
 InStream := TFileStream.Create(FileList[I], fmOpenRead);
 try
 if I = 0 then
 FileStream.CopyFrom(InStream, InStream.Size)
 else if InStream.Size>44 then
 begin
 InStream.Position := 44;
 FileStream.CopyFrom(InStream, InStream.Size - 44);
 end;
 finally
 InStream.Free;
 end;
 end;
 FileStream.Position := 4;
 FileSize := FileStream.Size - 8;
 FileStream.WriteBuffer(FileSize, SizeOf(FileSize));
 FileStream.Position := 40;
 FileSize := FileStream.Size - 44;
 FileStream.WriteBuffer(FileSize, SizeOf(FileSize));
end;

procedure TConcatWave.Execute;
begin
  JoinWavesToFile;
end;

end.