Playing a MIDI File

[The feature associated with this page, MCI, is a legacy feature. It has been superseded by MediaPlayer. MediaPlayer has been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer instead of MCI, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The following example opens a MIDI sequencer device, verifies that the MIDI mapper was selected as the output port, plays the MIDI file specified by the lpszMIDIFileName parameter, and closes the device after playback is complete. It uses the mciSendCommand function.

// Plays a specified MIDI file by using MCI_OPEN and MCI_PLAY. Returns 
// as soon as playback begins. The window procedure function for the 
// specified window will be notified when playback is complete. 
// Returns 0L on success; otherwise, it returns an MCI error code.

DWORD playMIDIFile(HWND hWndNotify, LPSTR lpszMIDIFileName)
{
    UINT wDeviceID;
    DWORD dwReturn;
    MCI_OPEN_PARMS mciOpenParms;
    MCI_PLAY_PARMS mciPlayParms;
    MCI_STATUS_PARMS mciStatusParms;
    MCI_SEQ_SET_PARMS mciSeqSetParms;

    // Open the device by specifying the device and filename.
    // MCI will attempt to choose the MIDI mapper as the output port.
    mciOpenParms.lpstrDeviceType = "sequencer";
    mciOpenParms.lpstrElementName = lpszMIDIFileName;
    if (dwReturn = mciSendCommand(NULL, MCI_OPEN,
        MCI_OPEN_TYPE | MCI_OPEN_ELEMENT,
        (DWORD_PTR)(LPVOID) &mciOpenParms))
    {
        // Failed to open device. Don't close it; just return error.
        return (dwReturn);
    }

    // The device opened successfully; get the device ID.
    wDeviceID = mciOpenParms.wDeviceID;

    // Check if the output port is the MIDI mapper.
    mciStatusParms.dwItem = MCI_SEQ_STATUS_PORT;
    if (dwReturn = mciSendCommand(wDeviceID, MCI_STATUS, 
        MCI_STATUS_ITEM, (DWORD_PTR)(LPVOID) &mciStatusParms))
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }

    // The output port is not the MIDI mapper. 
    // Ask if the user wants to continue.
    if (LOWORD(mciStatusParms.dwReturn) != MIDI_MAPPER)
    {
        if (MessageBox(hMainWnd,
            "The MIDI mapper is not available. Continue?",
            "", MB_YESNO) == IDNO)
        {
            // User does not want to continue. Not an error;
            // just close the device and return.
            mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
            return (0L);
        }
    }

    // Begin playback. The window procedure function for the parent 
    // window will be notified with an MM_MCINOTIFY message when 
    // playback is complete. At this time, the window procedure closes 
    // the device.
    mciPlayParms.dwCallback = (DWORD_PTR) hWndNotify;
    if (dwReturn = mciSendCommand(wDeviceID, MCI_PLAY, MCI_NOTIFY, 
        (DWORD_PTR)(LPVOID) &mciPlayParms))
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }

    return (0L);
}