start of file...
&0: sample list: 32 32-bit entries giving starts of sample numbers - all entries have a set value added to them, but as the first entry must point to the start of the file, this value can be eliminated by subtracting the first entry from everything
&80: 4 unused bytes
&84: instrument list: 255 32-bit entries giving starts of instrument numbers relative to start of file
&480: song speed list, standard format, always 32 subsongs
&4C0: instrument priority list, standard format, always 255 instruments
&6BE: sequence list for channel 1 - 32 32-bit entries giving offsets of sequence data from start of file
&73E: sequence list, channel 2
&7BE: sequence list, channel 3
&83E: sequence list, channel 4
&8BE: pattern list - 254 32-bit entries giving pattern offsets from start of file

patterns: standard format
instruments: standard format, except all command numbers are multiplied by 4
sequence: standard format