Hi,
To do that, you have to know what are the FM spec of the ad-lib engine.
The chip used is the YMF262.
I just had a look at the spec (pdf can be found), looks like it's a 4 operator FM synth.
So use 4 operator algo.
I read quickly so I maybe wrong, but it seems it only has one Amplitude enveloppe.
So your carrier operator(s) must have the same enveloppe (can be copied with the PC editor).
( hold button 3 (preenfm2) to modify the env of all operators at the same time / in the
tips here).
And the modulator enveloppes must be very simple : value 1 all the time.
Amplitude modulation or vibrato can be done with the matrix modulation.
And i think you can add a little noise (by using more operators) and use the "crusher" effect to get a slighty dirtier sound if that's what you're after.
So no miracle recipe but you need to know how this card works to mimic the sound.