Windows – How is media player playing midi .mid files

According to this recent question Stop Windows Media Player showing synchronization dialogue when USB device plugged the trick is to let it partially sync so that you get the WMPInfo.xml file created on your device (and leave it there), you can then go into WMP's options and your device will be listed along with the options uncheck "Start sync when device connects".

The questioner was asking about WMP11 on XP, but I've confirmed that this also works with WMP11 on Vista. Haven't had a chance to try it on my Win7 machine at home yet, but it does look very likely to work.

MP4 is just a file format. It describes how data is packed into a file, but doesn't tell you how it's been compressed. Your file uses video codec that is supported by your players and an audio codec which is not. Your players can't decode sound. That's also the reason why you don't hear sound after splitting the file - the program you used didn't support that codec, so it has just ommited sound entirely.

As @BrunoPereira suggested in the comments, you can use MediaInfo to get some details about the codec used.