uses MMSystem;

procedure TForm1.Button1Click(Sender: TObject);
var
  vol: longint;
  LVol, RVol: integer;
begin
  AuxGetVolume(ListBox1.ItemIndex, @Vol);
  LVol := Vol shr 16;
  if LVol < MaxWord - 1000 then
    LVol := LVol + 1000
  else
    LVol := MaxWord;
  RVol := (Vol shl 16) shr 16;
  if RVol < MaxWord - 1000 then
    RVol := RVol + 1000
  else
    RVol := MaxWord;
  AuxSetVolume(ListBox1.ItemIndex, LVol shl 16 + RVol);
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  i: integer;
  cap: TAuxCaps;
begin
  for i := 0 to auxGetNumDevs - 1 do
  begin
    auxGetDevCaps(i, Addr(cap), SizeOf(cap));
    ListBox1.Items.Add(cap.szPname)
  end;
end;