INT 66 - IBMSND driver - PLAY 8-BIT DIGITIZED SOUND
        AX = 0688h
        DS:SI -> SNDSTRUC (see below)
Return: ???
Program: The IBMSND driver is part of John W. Ratcliff's
           The IBM Digitized Sound Package
Note:   the installation check consists of looking for a valid signature
          string six bytes prior to the interrupt handler; this string may
          be either "KERN" or "MIDI" (in the latter case, call AX=0701h to
          determine whether IBMSND is installed)
SeeAlso: AX=068Bh,AX=068Fh,AX=0701h

Format of SNDSTRUC:
Offset  Size    Description
 00h    DWORD   -> audio data
 04h    WORD    length of audio data in bytes
 06h    DWORD   -> playback status flag
 0Ah    WORD    playback frequency

.