Just in case anyone comes across this thread, I wanted to make one more reply and it may also help you in resolving this issue.
Midi files are not true audio files and will not behave like MP3's or other true audio formats. Midi files are not a super compressed audio file. They are nothing more than a set of instructions telling the computer what sounds to generate. That's why the files are so small in size. You may find the information in this article I found very interesting.
If you want to use these files, they will need to be converted into a true audio format such as MP3. I found a free converter that does a nice job and will do the files in batches. I have attached it as a ZIP file.
Hope this helps you and anyone else who my see this.