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;