This is a patch that adds the FM Sound capability back into Ys for the Sega Master System that was taken out when it was translated into English for the US and Europe. In Japan the FM Sound module was originally an optional hardware upgrade for the Sega Mark III (basically the same exact thing we got as the Sega Master System), so many games like Ys supported not only regular PCM music but also the vastly superior FM Sound module. When the games were ported to other territories the FM Sound capability was usually disabled or completely removed.
I’ve also changed all the names back to their proper Ys names, so no more playing through the whole game as ARON instead of Adol.