The modMessage entry-point function for MIDI output drivers can optionally support the following messages, depending on the capabilities of the target hardware.
MODM_GETVOLUME | Requests the current volume level setting. This message is used only by internal synthesizer devices. |
MODM_PREPARE | Requests that the driver prepare a data block for playback. |
MODM_SETVOLUME | Sets the volume level. This message is used only by internal synthesizer devices. |
MODM_UNPREPARE | Requests that a driver clean up the preparation previously done on a data block. |