Thanks to a comment made by Maria on my blog, I tried installing the new version of OSS drivers, and am happy to say that the sound now works in OpenSolaris in VirtualBox on Mac OS X! Thanks, Maria!
Here's what I did:
# pkgrm oss (to delete the old version I installed previously)# rebootDownload the new oss driver file, oss-solaris-v4.0-1016-i386.pkg, from www.4front-tech.com/download.cgi
(select Solaris 10/11 x86/AMD64 in the list).
# pkgadd -d oss-solaris-v4.0-1016-i386.pkg# rebootRun osstest after the OS comes back up, and listen to the music! Sounds great.
UPDATE 8/13/08: I think I spoke too soon. The sound is very flaky, sometimes works, sometimes doesn't. I am not sure what is happening.