Puato, while your example does provide synth music, it is not quite FM-synthesis per se... although it comes pretty close, in some instances.
Here are a couple of excellent examples for pure FM-synthesis being done accurately right that we are looking for, as these ones from Ultima VI: The False Prophet and Ultima Underworld II clearly show, and please pay *very* close attention to the many instruments being used as were shown thoroughly through an AdLib FM-synth soundcard on which those original games were first created on MS-DOS PCs from within the early 1990s:
...and please let them inspire you richly in creating your own original music for your game project here. ;)
I am absolutely most glad to be able to help you out again, Puato, and perhaps that should enable you even further to finally get your completed game project done as an official new entry into my Wide-Dot Pixel Game Jam 2017 on time before the deadine expires. Thank you so much once more!!! ^-^=b !!