Oerg866 wrote:TmEE co.(TM) wrote:I only said you can approximate it as that sound is a very basic FM sound...
Exactly

but I love it!

In general, we all should appreciate the origin of such epic sounds much more

You can use a DX7 as a 4 Operator Device - just switch the Operators off. Search for specific Patches or create a Patch using some Software.
The next to consider is the available Algorithms - check that they both have the same Algorithms and start out using a very simple one first.
I'd advise you to read about FM-Synthesis - even if you understand AM - which most People can understand through the Time-Domain, very few People understand FM as very few People 'think' in the Freq-Domain.
Get yourself a copy of Chowning's Book:
Fm Theory and Applications: By Musicians for Musicians by John Chowning.
You can find it easily as it was published widely.
YM2413 has only one Voice - so you're immediately limited but it would help you to understand. If you pick up the 'Complete DX7' you'll find that the Tutorials start from the absolute basics - and this is the way to approach FM-Synthesis.
*By 'only one Voice' I mean that the rest of the Instruments load in Preset-Voices - leaving the last one as user defined.
Best of Luck.