INT 66 - IBM Digitized Sound Package MIDI driver - GET DIGITIZED SOUND CAPABIL
        AX = 0701h
Return: AX = digitized sound capabilities
            0000h if digitized sound driver (functions 06xxh) not available
Note:   the installation check for the MIDI driver is to test for the signature
          "MIDI" six bytes before the interrupt handler
SeeAlso: AX=0688h

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