The widMessage entry-point function for waveform input drivers must support the following messages.
| WIDM_ADDBUFFER | Adds a buffer to the input queue. |
| WIDM_CLOSE | Closes and deallocates a waveform input device. |
| WIDM_GETDEVCAPS | Requests the capabilities of a waveform input device. |
| WIDM_GETNUMDEVS | Requests the number of waveform input devices a driver supports. |
| WIDM_GETPOS | Requests the current input recording position. |
| WIDM_OPEN | Opens and allocates a waveform input device. |
| WIDM_RESET | Stops waveform input and returns all data buffers to the client application. |
| WIDM_START | Begins waveform input. |
| WIDM_STOP | Ends waveform input. |