MidiInProc callback function

The MidiInProc function is the callback function for handling incoming MIDI messages. MidiInProc is a placeholder for the application-supplied function name. The address of this function can be specified in the callback-address parameter of the midiInOpen function.


void CALLBACK MidiInProc(
   HMIDIIN   hMidiIn,
   UINT      wMsg,
   DWORD_PTR dwInstance,
   DWORD_PTR dwParam1,
   DWORD_PTR dwParam2


  • hMidiIn
    Handle to the MIDI input device.

  • wMsg
    MIDI input message.

  • dwInstance
    Instance data supplied with the midiInOpen function.

  • dwParam1
    Message parameter.

  • dwParam2
    Message parameter.

Return value

This function does not return a value.


The meaning of the dwParam1 and dwParam2 parameters is specific to the message type. For more information, see the topics for messages, such as MIM_DATA.

Applications should not call any multimedia functions from inside the callback function, as doing so can cause a deadlock. Other system functions can safely be called from the callback.


Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]


Mmsystem.h (include Windows.h)

See also

MIDI Functions