You must open a MIDI device before using it, and you should close the device as soon as you finish using it. Windows provides the following functions to open and close different types of MIDI devices:
| midiInClose | Closes a specified MIDI input device. |
| midiInOpen | Opens a specified MIDI input device for recording. |
| midiOutClose | Closes a specified MIDI output device. |
| midiOutOpen | Opens a MIDI output device for playback. |
Each function that opens a MIDI device takes as parameters a device identifier, an address of a memory location, and some parameters unique to MIDI devices. The memory location is filled with a device handle, which is used to identify the open audio device in calls to other audio functions.
Many MIDI functions can accept either a device handle or a device identifier. Although you can use a device handle wherever you would use a device identifier, you cannot always use a device identifier when a handle is called for.
Note MIDI devices are not necessarily shareable, so a particular device may not be available when a user requests it. If this happens, the application should notify the user and allow the user to try to open the device again.