Comment by sparky_z

Completely separate companies, both called Yamaha. One was spun off from the other, but I don't think there was ever a time when the same company sold both. (Basically, the musical instrument company was redirected to making war materiel during WWII. After the war, they didn't want to just throw away all of their new industrial capacity so they spun off a company to make use of all their new equipment and expertise and then went back to making instruments.)