I strongly suggest a system which allows people to search for specific filetypes if they want to (such as an "advanced search" field under which one could enter file extensions (such as WAV, PDF, or OGG) and only those files would show up as results. Please, please, please, do that. It would be infinitely helpful to those who are searching for the kind of music or ebook format of their preference. (For example, it's very annoying to have to sort by type for every audio search I do; if I could have specific file extenson(s) be the only ones which showed up, it would stop my endless scrolling and sorting by type.)