This is an ongoing headscratcher. If someone has a simple explanation I'd like to hear it.
Q: What do search engines want with .midi (sound) files?
I looked it up. The extension isn't used for anything else. There is no Sound Search. ("Google Play" is something else. What exactly I'm not sure: their answer to iTunes?) ".midi" is not one of the options on the File Type dropdown in Advanced Search.
You can use the word "midi" in a search string-- I've seen it-- but the search engine wouldn't need to GET the file. A simple HEAD is enough to confirm that it exists.
I guess I should be glad the robotic brain understands that it doesn't need to include a .dmg, .zip or .sit in a preview. Those are sized in megabytes. A .midi is just a few bytes.
What do they do with them?