Beni Tracker module format:

The file extension .PIS is used since the previous incarnation
of Beni Tracker was called "Psychisch Tracker" (unreleased).

Offset   Bytes    Description
------   -----    -----------
0        1        Song length
1        1        N. of patterns
2        1        N. of instruments
3        ?        Pattern map (N. of patterns * 1 byte)
?        ?        Instrument map (N. of instruments * 1 byte)
?        ?        Order list (Song length * 9 bytes)
?        ?        Pattern data (N. of patterns * 192 bytes)
?        ?        Instrument data (N. of instruments * 11 bytes)
?        4        "B.J." (v1.8 identification mark)

-Pattern and instrument maps
   PIS, the intelligent format it is, saves only the
   patterns and instruments that are used. The maps
   therefor contain for each pattern (instrument) in
   the file the number that was used for it during editing.
   Eg. if You have this in Your (otherwise empty) order list:
      02
      04
      00
   The pattern map, containing the indices of used patterns
   in ascending order, will look like this:
      ptnmap[0]=0
      ptnmap[1]=2
      ptnmap[2]=4
   Ergo, the maps contain the order in that the patterns
   (instruments) are saved in the data blocks below.

-Pattern data format
   A pattern consists of 64 * 3 bytes where 3 bytes encode
   one note as:

      nnnn.... ........ ........
      ....ooo. ........ ........
      .......i iiii.... ........
      ........ ....eeee eeeeeeee

   n = note (0..12) as index into frequency table, 12 is blank
   o = octave
   i = instrument
   e = effect

-Instrument format
   An instrument consists of 11 bytes.

   Offset   Description
   ------   -----------
   0        Op.1: Multiple/EG type/Vibrato/Amp.mod.
   1        Op.2:                 "
   2        Op.1: Output level
   3        Op.2:    "     "
   4        Op.1: Attack/Decay
   5        Op.2:       "
   6        Op.1: Sustain/Release
   7        Op.2:        "
   8        Op.1: Waveform
   9        Op.2:     "
   10       Feedback/Connection type

-"B.J."
   To let v1.8 distinguish between module formats. Has absolutely
   no effect when loaded in v1.3.