procedure redraw2;
var i, YPos: LongInt;
     YVal : Single;
     FFTData : TFFTData;
begin
BASS_ChannelGetData(TabSon[1].GetStream, @FFTData, BASS_DATA_FFT1024);
Form1.DXDraw1.surface.Canvas.Pen.Color := ClAqua;
   for i := 0 to 95 do
     begin
     YVal := Abs(FFTData[i + 5]);
     YPos := Trunc((YVal) * 500); //Тут ошибка.
     Form1.DXDraw1.Surface.Canvas.MoveTo(11 + i, 300);
     Form1.DXDraw1.Surface.Canvas.LineTo(11 + i, 300 - YPos);
     end;
end;

Function MyTrunc(X: Single): LongInt;
Var i: LongInt;
begin
   For i:=0 to 40 do
     If X > i then result := i;
   If X > 40 then result := 40;
end;

procedure redraw3(FFTData : TFFTData; X, Y : Integer);
         var i, YPos, DrawPoint : LongInt; YVal : Single;
        begin
         Form1.DXDraw1.Surface.Canvas.Pen.Color := clAqua;
          for i := 0 to 128 do begin
            YVal := Abs(FFTData[(i * 1) + 5]);
            if YVal > 40 then YVal := 40;
            YPos := MyTrunc(YVal);
            if YPos > 40 then YPos := 40;
            DrawPoint := YPos;
            begin
              Form1.DXDraw1.Surface.Canvas.MoveTo(X + i, Y + 40);
              Form1.DXDraw1.Surface.Canvas.LineTo(X + i, Y + 40 - DrawPoint);
            end;
          end;
end;