Commit 9e1008f13735 added mmioSeek call that skips the whole data portion of the RMID chunk, breaking the handling of RMID (RIFF-based MIDI) files as it effectively skips the whole content of the RIFF file. Since mmioDescend expects the file position to be somewhere within the specified parent chunk, it's guaranteed to fail.
$ WINEDEBUG=+mcimidi wine wintest.exe mcishell mci.c:178: Type your commands to the MCI, end with Ctrl-Z/^D open BOSSNOVA.RMI mci.c:188: command: open BOSSNOVA.RMI 0764:trace:mcimidi:MIDI_mciOpen (1, 00000200, 0051FB98) 0764:trace:mcimidi:MIDI_mciOpen wDevID=1 (lpParams->wDeviceID=1) 0764:trace:mcimidi:MIDI_mciOpen MCI_OPEN_ELEMENT L"bossnova.rmi"! 0764:trace:mcimidi:MIDI_mciOpen hFile=00000001 0764:trace:mcimidi:MIDI_mciOpen ParentChunk ckid=RIFF fccType=RMID cksize=000052DA mci.c:191: Test failed: mci open BOSSNOVA.RMI error: 296(40 MCIERR_INVALID_FILE)
Its introduction seems unrelated to the rest of that commit and there's no reason given for placing it there, so let's remove the mmioSeek call to fix RMID file handling in MCI. Previous mmioDescend call will set the position to just after the chunk's form type, which is exactly where it should be when calling mmioDescend the second time to find the data chunk. Other parts of Wine code that deal with RIFF files don't seek in analogous situations either.
Fixes: 9e1008f13735 ("Removed fixed size array to store specific data")