Links to official Yamaha keyboard software, manuals, sample files, etc. are at this page.
However, some years ago many pages including software products (e.g. programs and MIDI files) and technical stuff (e.g. tutorials and specifications) were removed. But, cheer up!
With help from "The Wayback Machine" I have located many of these removed pages.
They still look the way they did; and most software products and technical stuff are still there!
Click a link and be directed to "The Wayback Machine" search result page; and then select the version of the web page to examine.