Ç PSG

   This  is  log  file  produced  by  X128 (ZX Spectrum emulator) and fMSX (MSX
emulator). Every access to the AY 3-891x (Yamaha's soundchip) is stored in this
file. It's much like RAW format for adlib.
   format1:  [0]=db     'PSG',1ah                  ... file identifier
             [4]=db     data                       ... AY data
   data: command or parameter  command==0-15,byte  ... next byte is data for
                                                       this AY register
                               command==0fdh       ... eom (end of music)
                               command==0feh,byte  ... multiple eoi
                               command==0ffh       ... eoi (end of interrupt,
                                                       current data will be
                                                       send to ay-emulator)

   You can also use utility PSG2.EXE to convert PSG music to another format:
   format2:  [0]=db     'PSG2'    ... file identifier
             [4]=struct data      ... AY data
   data: change_map (word)        ... bit-map specifying which regs will be
                                      changed in this interrupt. Order: L->R
                                      (when 0ffffh, end of music)
         map_size (byte)          ... specifies how many times currently
                                      defined map will be used (ie. how many
                                      times will be data send in this form)
         data (bytes)             ... data for registers, reg. 0 comes first
                                      After receiving all changes for current
                                      interrupt, data are sent to ay-emu.
                                      Map_size is decremented and when not 0,
                                      next interrupt use same change_map as
                                      previous one.