This is yet another tricky issue... The different versions of SPUTM (the SCUMM presentation utility) have LOTS of differences between the different major versions. To sum those up:
MI1 disk versions: 4
MI1 CDROM versions: 5
CMI (only Windows-based SPUTM): 8
To get DirectSound support with an original SPUTM engine thus requires use of the CMI engine. That one is so different that a simple patch won't do the trick.
If you want the reasons, read on, if you just want some kind of solution look at the bottom.
1. The graphics need to be scaled up to double size (and either changed in aspect ratio with interpolation or have 80 lines added to the bottom, since we're going from 320x200 to 640x480).
2. The scripts need MAJOR changes. The CMI script interpreter is totally different from the MI1/MI2 interpreters. This includes different compiled code, different variable sizes etc. Not only that, but a lot of scripts would have to be actually rewritten due to the different ways the two engines work.
3. CMI doesn't have a MIDI version of iMUSE. Only digital music can be played back. And MI1/2 don't provide such.
4. The costumes (character animations) need to be rebuilt. The old games use the COST format, the new games use the AKOS format.
5. Just about every other block in the games must be rebuilt (and the bundles need to be restructured), because just about every block format has changed since MI2, although not as much as the blocks mentioned above.
6. Probably more than that. This was what I could come up with in 4 minutes
*** SOME KIND OF SOLUTION ***
I have two solutions handy:
1. Have you tried scummvm? (http://scummvm.sourceforge.net
2. Have you tried Quick & Easy (or tried fooling around with VDMSound yourself (search for it)? Quick & Easy is hosted here on Mojo somewhere, it doesn't have a homepage, though.
Hope this helps, or at least explains why it doesn't