Excerpt from Adlmidi for extracting instruments from ESS FM driver. Not a pretty sight, and they don't really work anyway.

gen_adldata.cc

// LoadESFM("drivers/es1969.sys", 35904, 64, "esfm");

static void LoadESFM(const char* fn, size_t file_offset, unsigned bank, const char* prefix)
{
    FILE* fp = std::fopen(fn, "rb");
    std::fseek(fp, file_offset, SEEK_SET);
    std::vector<unsigned char> data(28 * 256);
    std::fread(&data[0], 1, data.size(), fp);
    std::fclose(fp);
    
    for ( unsigned a = 0; a < 256; ++a )
    {
        unsigned offset = a * 28;
        unsigned gmno = a;
        int midi_index = gmno < 128 ? gmno : gmno - 128;
        
        insdata tmp, tmp2;
        
        tmp.data[0] = data[offset + 0];
        tmp.data[1] = data[offset + 5];
        tmp.data[2] = data[offset + 2];
        tmp.data[3] = data[offset + 7];
        tmp.data[4] = data[offset + 3];
        tmp.data[5] = data[offset + 8];
        tmp.data[6] = data[offset + 4];
        tmp.data[7] = data[offset + 9];
        tmp.data[8] = data[offset + 1];
        tmp.data[9] = data[offset + 6];
        tmp.data[10] = data[offset + 24];
        tmp.finetune = 0; //data[offset + 12];

        tmp2.data[0] = data[offset + 10];
        tmp2.data[1] = data[offset + 15];
        tmp2.data[2] = data[offset + 12];
        tmp2.data[3] = data[offset + 17];
        tmp2.data[4] = data[offset + 13];
        tmp2.data[5] = data[offset + 18];
        tmp2.data[6] = data[offset + 14];
        tmp2.data[7] = data[offset + 19];
        tmp2.data[8] = data[offset + 11];
        tmp2.data[9] = data[offset + 16];
        tmp2.data[10] = data[offset + 25];
        tmp2.finetune = 0; //data[offset + 12];
        
        struct ins tmp3;
        tmp3.notenum   = 0;
        tmp3.pseudo4op = false;
        
        std::string name;
        if(midi_index >= 0) name = std::string(1,'\377')+MidiInsName[midi_index];
        
        char name2[512]; sprintf(name2, "%s%c%u", prefix,
                                 (gmno<128?'M':'P'), gmno&127);
        
        size_t resno = InsertIns(tmp,tmp2,tmp3, name, name2);
        SetBank(bank, gmno, resno);
    }
}