It has been told many times, but here it is once again.
DOSBox OPL cores are inaccurate while NukedOPL is 1:1 with the hardware.

I basically created a white noise using maximum feedback into square wave as the instrument in Adlib Tracker 2 and played it through various OPL cores.
The fast core which is the default in DOSBox is completely whacked, while compat core is also far from accurate.
* All tested at 49716Hz sampling rate.