[[cHackAll]]

Código Delphi [-]
uses Windows, Messages, MMSystem, Types; // by cHackAll

var
 Buffer: array [0..31] of Byte;
 hWnd, hCanvas, hBrush, hWhite, hGray: Cardinal;
 WaveInHdr: TWaveHdr = (lpData: @Buffer; dwBufferLength: SizeOf(Buffer));

function WndProc(hWnd, Msg, wParam, lParam: Integer): Integer; stdcall;
var PaintStruct: TPaintStruct;
begin
 Result := 0;
 case Msg of
  WM_ERASEBKGND: Result := 1;
  WM_PAINT: begin
             BeginPaint(hWnd, PaintStruct);
             BitBlt(PaintStruct.hdc, 0, 0, SizeOf(Buffer) * 3, $FF, hCanvas, 0, 0, SRCCOPY);
             EndPaint(hWnd, PaintStruct);
            end;
  WM_DESTROY: PostQuitMessage(0);
 else
  Result := DefWindowProc(hWnd, Msg, wParam, lParam);
 end
end;

procedure waveInProc(waveIn, uMsg, dwInstance, lParam, wParam: Cardinal); stdcall;
begin
 if uMsg = WIM_DATA then
  begin
   waveInAddBuffer(waveIn, PWaveHdr(lParam), SizeOf(TWaveHdr));
   FillRect(hCanvas, Rect(0, 0, SizeOf(Buffer) * 3, $FF), hBrush);
   SelectObject(hCanvas, hGray);
   waveIn := SizeOf(Buffer);
   repeat Dec(waveIn);
    if Abs(Buffer[waveIn] - 128) = 1 then Buffer[waveIn] := 128;
    MoveToEx(hCanvas, waveIn * 3, 0, nil);
    LineTo(hCanvas, waveIn * 3, $FF);
   until waveIn = 0;
   SelectObject(hCanvas, hWhite);
   waveIn := High(Buffer);
   MoveToEx(hCanvas, waveIn * 3, Buffer[waveIn], nil);
   repeat Dec(waveIn);
    LineTo(hCanvas, waveIn * 3, Buffer[waveIn]);
   until waveIn = 0;
   repeat
    if Abs(Buffer[waveIn] - 128) > 1 then
     begin
      MoveToEx(hCanvas, waveIn * 3, 128, nil);
      LineTo(hCanvas, waveIn * 3, Buffer[waveIn]);
     end;
    Inc(waveIn);
   until waveIn = SizeOf(Buffer);
   InvalidateRect(hWnd, nil, True);
  end;
end;

var
 hScreen, waveIn: Cardinal;
 WndClass: TWndClass = (lpfnWndProc: @WndProc; cbWndExtra: 4; lpszClassName: 'Waves');

 Rect: TRect;
 Value: Cardinal = 0;
 Controls: array [0..1] of TMixerControl;
 MixerLine: TMixerLine = (cbStruct: SizeOf(TMixerLine); dwDestination: 1; dwComponentType: MIXERLINE_COMPONENTTYPE_DST_WAVEIN);
 LineControls: tMixerLineControls = (cbStruct: SizeOf(TMixerLineControls); dwControlType: MIXERCONTROL_CONTROLTYPE_VOLUME; cbmxctrl: SizeOf(TMixerControl); pamxctrl: @Controls);
 Details: TMixerControlDetails = (cbStruct: SizeOf(TMixerControlDetails); cChannels: 1; cbDetails: SizeOf(Value); paDetails: @Value);
 FormatEx: TWaveFormatEx = (wFormatTag: WAVE_FORMAT_PCM; nChannels: 2; nSamplesPerSec: 100; nAvgBytesPerSec: 100; nBlockAlign: 1; wBitsPerSample: 8);
 Msg: TMsg;

begin
 hScreen := GetDC(0);
 hCanvas := CreateCompatibleDC(0);
 SelectObject(hCanvas, CreateCompatibleBitmap(hScreen, SizeOf(Buffer) * 3, $FF));
 hWhite := CreatePen(PS_SOLID, 1, $FFFFFF);
 hGray := CreatePen(PS_SOLID, 1, $404040);
 ReleaseDC(0, hScreen);

 WndClass.hCursor := CreateCursor(HInstance, 5, 5, 9, 9, PChar(#255#255#255#255#255#255#255#255#247#255#255#255#255#255#255#255#255#255), PChar(#8#8#8#8#8#8#28#28#255#128#28#8#8#8#8#8#8#0));
 RegisterClass(WndClass);
 hBrush := CreateSolidBrush(0);
 hWnd := CreateWindowEx(WS_EX_TOOLWINDOW + WS_EX_LAYERED, WndClass.lpszClassName, WndClass.lpszClassName, WS_VISIBLE, 0, 0, 0, $FF, 0, 0, hInstance, nil);
 GetClientRect(hWnd, Rect);
 SetWindowPos(hWnd, HWND_TOPMOST, 6, 6, SizeOf(Buffer) * 3 + 4, $FF + ($FF - Rect.Bottom), 0);
 SetLayeredWindowAttributes(hWnd, 0, 224, LWA_ALPHA);

 mixerOpen(@waveIn, 0, 0, 0, MIXER_OBJECTF_WAVEIN);
 mixerGetLineInfo(waveIn, @MixerLine, MIXER_GETLINEINFOF_COMPONENTTYPE);
 LineControls.dwLineID := MixerLine.dwLineID;
 LineControls.cControls := MixerLine.cControls;
 mixerGetLineControls(waveIn, @LineControls, MIXER_GETLINECONTROLSF_ALL);
 Details.dwControlID := Controls[0].dwControlID;
 Value := Byte(Controls[0].dwControlType = MIXERCONTROL_CONTROLTYPE_VOLUME) * $FFFF;
 MixerSetControlDetails(waveIn, @Details, MIXER_SETCONTROLDETAILSF_VALUE);
 Details.dwControlID := Controls[1].dwControlID;
 Value := Byte(Controls[1].dwControlType = MIXERCONTROL_CONTROLTYPE_VOLUME) * $FFFF;
 MixerSetControlDetails(waveIn, @Details, MIXER_SETCONTROLDETAILSF_VALUE);
 mixerClose(waveIn);

 waveInOpen(@waveIn, WAVE_MAPPER, @FormatEx, Cardinal(@WaveInProc), HInstance, CALLBACK_FUNCTION);
 waveInPrepareHeader(waveIn, @WaveInHdr, SizeOf(WaveInHdr));
 waveInAddBuffer(waveIn, @WaveInHdr, SizeOf(WaveInHdr));
 waveInStart(waveIn);

 repeat GetMessage(Msg, 0, 0, 0);
  DispatchMessage(Msg);
 until Msg.message = WM_QUIT;
end.

Esta es una pequeña prueba que creé hace algún tiempo, es un osciloscopio (scope ~ oscilloscope), de la salida de sonido. No funciona adecuadamente en algunos ordenadores pero en la mayoría si. Tampoco esta "afinada" pero cuanto tenga más tiempo libre lo haré!

Nota; El Stereo Mix NO debe estar en silencio. Les adjunto la fuente compilada para que lo prueben en caso de no poder compilarlo.

PD; Espero ésto deje de ser un monologo

Saludos