Format of GeneralDeviceClass structure:
Offset	Size	Description	)
 00h	4 BYTEs	name of the structure ("GENI")
 04h	DWORD	structure length
 08h	WORD	type of device (1=Wave, 2=MIDI)
 0Ah	WORD	version of VESA driver support (0100h for 1.00)
 10h	var	for CX=handle for Wave device:
		    Wave Info structure (see #00113)
		    some bytes ???
		for CX=handle for MIDI device:
		    MIDI Info Structure (see #00118)
		    first 8 bytes of MIDI Service Structure ???
SeeAlso: #00122,#00124