[Bargest]

Код:

procedure UpdateSpectrum(uTimerID, uMsg, dwUser, dw1, dw2 : Integer); stdcall;
begin
  if isPlayed then
  begin
    OnDrawData;
    OnDrawBar;
    OnDrawWave;
  end;
end;

Вся отрисовка внутри этих функций видимо.
UPD:

Код:

MoveToEx(BarBitmap.DC, I * (ColWidth + 2) + Offset, BarBitmap.aHeight - fftPeaks[i], NIL);
      LineTo(BarBitmap.DC, I * (ColWidth + 2) + ColWidth + Offset, BarBitmap.aHeight - fftPeaks[i]);

      SetRect(aRect, I * (ColWidth + 2) + Offset, BarBitmap.aHeight - FFTFallOff[i], I * (ColWidth + 2) + ColWidth + Offset, BarBitmap.aHeight);
      SetRect(bRect, aRect.Left, BarBitmap.aHeight, aRect.Right, BarBitmap.aHeight - 1);

      J := aRect.Bottom - aRect.Top;
      repeat
        B := 0;
        R := 255 div BarBitmap.aHeight * (aRect.Bottom - aRect.Top - J);
        G := 256 - R;
	FillRect(BarBitmap.DC, bRect, RGB(R, G, B));
	OffsetRect(bRect, 0, -1);
        dec(J);
      until J < 0;