For GXSCC you can, but quite a lot of precision will be lost in the process; GXSCC uses very long ADSR volume envelopes (that has higher precision than SCC itself does), and its waveforms are 8-bit (FDS uses 6, N163 uses 4). Assuming Beta 236 is used, The SCC waveforms are located at 0x51158, each containing 8 bytes of what appears to be some average value, 32 bytes of the wave name, and 32 unsigned bytes of the waveform itself (this is how the SCC works). The instrument mapping is located at 0x53DAC, containing 128 integers for each of the 8 instrument sets available in GXSCC; the volume envelopes are located at 0x551B0, each containing 5 integers:
- Attack duration, in samples; (if you use different sample rates for GXSCC, its volume envelopes will scale with the sample rate)
- Decay duration, in samples;
- Sustain level, maximum is 0x0000FFFF;
- Release duration (after sustain), in samples;
- Release duration (after note off), in samples.
For GXOPLL it is even simpler: all its instruments are located at 0x50824, 8 bytes per instrument. Because VRC7 is a dumped-down version of OPLL, those patches work immediately when copied into the VRC7 instrument editor from a hex editor. In GXOPLL the instrument mapping for the melodic MIDI instruments is located at 0x5373C; by altering this table it is possible to use custom OPLL patches within GXOPLL, and neither OPLL nor GXOPLL will enforce one single custom patch for all channels since only VRC7 does that.
If you want to use these instruments losslessly, TriloTracker is a native tracker that uses the Konami SCC and the AY-3-8910. (A private beta version exists that uses the OPLL instead of SCC.) In particular, "METAL SIN" has appeared in many places under names such as "Konami Lead" or "Konami Organ".