Delphi - alguna ayuda con un reprod de musica

Hola gente necesito alguna ayuda para arreglar un reproductor de música que debo hacer.
La parte que debo arreglar es la de reproducción aleatoria continua y repetitiva, funciona cada uno pero no como tendría que ser. En algunos casos me aparece algo como error MCI y no se si esta bien como obtener el nombre del archivo en un Tlistbox(lbxz1)
cualquier ayuda se agradece.

el código es:



unit Unit5;

interface

uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls,
Vcl.ComCtrls, Vcl.MPlayer, Vcl.Menus,MMSystem;

type
TForm5 = class(TForm)
mp: TMediaPlayer;
progreso: TTrackBar;
tbvol: TTrackBar;
lbx1: TListBox;
OpenDialog1: TOpenDialog;
timer: TTimer;
MainMenu1: TMainMenu;
Archivo1: TMenuItem;
Abrir1: TMenuItem;
GuardarPlaylist1: TMenuItem;
CargarPlaylist1: TMenuItem;
Salir2: TMenuItem;
lbllen1: TLabel;
lbllen2: TLabel;
lbln: TLabel;
lblseek: TLabel;
SaveDialog1: TSaveDialog;
OpenDialog2: TOpenDialog;
lblpos1: TLabel;
lblpos2: TLabel;
tvol: TLabel;
Button1: TButton;
Rg: TRadioGroup;
procedure Salir2Click(Sender: TObject);
procedure Abrir1Click(Sender: TObject);
procedure timerTimer(Sender: TObject);
procedure GuardarPlaylist1Click(Sender: TObject);
procedure CargarPlaylist1Click(Sender: TObject);
procedure tbvolChange(Sender: TObject);
procedure lbx1DblClick(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure RgClick(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
// procedure CheckIfOpen;


end;

var
Form5: TForm5;
i,il,itel:integer;
s:String;
r:integer;
implementation

{$R *.dfm}


procedure TForm5.Abrir1Click(Sender: TObject);
var
slied,sname : string;
ip : integer;
begin
opendialog1.Execute;
slied := opendialog1.FileName;
mp.FileName:= slied;
mp.Open;
itel := mp.TrackLength[1];
timer.Enabled:=true;
lbllen1.Caption := IntToStr(((trunc(itel/1000))div 60)) + ':';
lbllen2.caption := IntToStr((trunc(itel/1000))mod 60);

if length(IntToStr((trunc(itel/1000))mod 60)) <> 2
then
lbllen2.Caption := '0' + IntToStr((trunc(itel/1000))mod 60);

sname := slied;

repeat
ip := pos('\',sname);
Delete(sname,1,ip);
until (ip =0);

lbln.caption := sname;

with progreso do
progreso.Max:=mp.Length;

lbx1.Items.Add(mp.FileName);
end;

procedure TForm5.Button1Click(Sender: TObject);
begin
lbx1.Clear;
end;

procedure TForm5.CargarPlaylist1Click(Sender: TObject);
begin
opendialog2.Execute;
lbx1.Items.LoadFromFile(opendialog2.FileName);
timer.Enabled := true;
lbx1.ItemIndex := 0;
i := lbx1.itemindex;
mp.FileName := lbx1.Items.Strings[i];
mp.Open;
end;


procedure TForm5.GuardarPlaylist1Click(Sender: TObject);
begin
savedialog1.Execute;
lbx1.Items.SaveToFile(savedialog1.FileName + '.amp');
end;

procedure TForm5.Salir2Click(Sender: TObject);
begin
Close;
end;

procedure TForm5.timerTimer(Sender: TObject);
begin
progreso.Position := mp.Position;
if progreso.Max>0 then
progreso.Position:=mp.Position;
itel := mp.Position;
lblpos1.Caption := IntToStr(((trunc(itel/1000))div 60)) + ':';
lblpos2.caption := IntToStr((trunc(itel/1000))mod 60);
if length(IntToStr((trunc(itel/1000))mod 60)) <> 2
then
lblpos2.Caption := '0' + IntToStr((trunc(itel/1000))mod 60);

if lblseek.Caption = 'Position:'
then progreso.Position := mp.Position;

if mp.Position = mp.TrackLength[1]
then begin
lbx1.ItemIndex := lbx1.ItemIndex + 1;
i := lbx1.ItemIndex;
mp.FileName := lbx1.Items.Strings[i];
mp.Open;
mp.Play;
s := mp.FileName;
repeat
il := pos('\',s);
Delete(s,1,il);
until (il =0);
lbln.Caption := s;

itel := mp.TrackLength[1];
lbllen1.Caption := IntToStr(((trunc(itel/1000))div 60)) + ':';
lbllen2.caption := IntToStr((trunc(itel/1000))mod 60);



end;
progreso.Max := mp.TrackLength[1];
end;

procedure TForm5.tbvolChange(Sender: TObject);
begin
waveOutSetVolume(WAVE_MAPPER,(tbvol.position-63488)*-1 shl 16 +(tbvol.position-63488)*-1);
end;

procedure TForm5.lbx1DblClick(Sender: TObject);
begin
timer.Enabled := true;
i := lbx1.ItemIndex;
mp.FileName := lbx1.Items.Strings[i];
mp.Open;
s := mp.FileName;
repeat
il := pos('\',s);
Delete(s,1,il);
until (il =0);
lbln.Caption := s;

itel := mp.TrackLength[1];
lbllen1.Caption := IntToStr(((trunc(itel/1000))div 60)) + ':';
lbllen2.caption := IntToStr((trunc(itel/1000))mod 60);
mp.Play;
end;

procedure TForm5.RgClick(Sender: TObject);
begin
case rg.ItemIndex of
0: begin
timer.Enabled := False; //continua
mp.Stop;
mp.Close;
lbx1.ItemIndex := lbx1.ItemIndex+1;
mp.FileName := lbx1.Items[Lbx1.ItemIndex];
mp.Open;
progreso.Max := mp.TrackLength[0];
mp.Play;
timer.Enabled:=True;
lbln.Caption:= lbx1.Items.Strings[lbx1.ItemIndex];
end;
1: begin
timer.Enabled := False; //aleatoria
mp.Stop;
mp.Close;
r := Random (lbx1.Items.Count);
lbx1.ItemIndex := r;
mp.FileName := lbx1.Items[Lbx1.ItemIndex];
mp.Open;
progreso.Max := mp.TrackLength[0];
mp.Play;
timer.Enabled := True;
lbln.Caption := lbx1.Items.Strings[lbx1.ItemIndex];
end;
2: begin
progreso.Max := mp.Length; //repetitiva
timer.Enabled := true;
mp.EnabledButtons := [tmpbtntype.btPause,tmpbtntype.btStop,tmpbtntype.btPlay];
mp.Play;
lbln.caption := extractfilename(mp.FileName)+' - '+extractfilename(mp.FileName);
end;
end;
end;

end.