The following table lists the messages that the DriverProc function in an ACM driver can receive, along with the operation the driver performs when it receives each message. Message definitions are contained in msacmdrv.h.
| Message | Operation Performed by Driver |
| ACMDM_DRIVER_ABOUT | Displays an About dialog box. |
| ACMDM_DRIVER_DETAILS | Returns information about the driver. |
| ACMDM_DRIVER_NOTIFY | Determines status changes in other drivers. |
| ACMDM_FILTER_DETAILS | Returns information about a filter. |
| ACMDM_FILTERTAG_DETAILS | Returns information about a filter tag (type). |
| ACMDM_FORMAT_DETAILS | Returns information about a format. |
| ACMDM_FORMAT_SUGGEST | Suggests an input or output format. |
| ACMDM_FORMATTAG_DETAILS | Returns information about a format tag (type). |
| ACMDM_HARDWARE_WAVE_CAPS_INPUT | Returns device input capabilities. |
| ACMDM_HARDWARE_WAVE_CAPS_OUTPUT | Returns device output capabilities. |
| ACMDM_STREAM_CLOSE | Closes a data stream. |
| ACMDM_STREAM_CONVERT | Performs conversion operations on supplied data, based on conversion parameters received by ACMDM_STREAM_OPEN. |
| ACMDM_STREAM_OPEN | Opens a data stream. Includes data conversion parameters. |
| ACMDM_STREAM_PREPARE | Prepares source and destination data buffers. |
| ACMDM_STREAM_RESET | Stops an asynchronous conversion operation. |
| ACMDM_STREAM_SIZE | Estimates the required size of a source or destination buffer. |
| ACMDM_STREAM_UNPREPARE | Removes preparation performed on source and destination data buffers. |