Up until now, KDE 4 users have had to use OSSv4 own sound mixer (ossxmix) to change volumes levels while within KDE. Recently though preliminary support for OSSv4 has been built into kmix.
Testing
The Open Source Sound system is a sound system for *nix operating systems built on the original OSS format. A number of users have requested OSSv4 support in kmix for the last year. OSSv4 has now been added to the trunk of the kmix svn. I compiled kmix and tested it.

And it works pretty good.
I’ve built a PKGBUILD for Arch linux. If you’d like to compile it take a look at that for instructions.
What doesn’t work
- Multimedia keys won’t be able to change volume and if you push them enough kmix magically disappears.
- No support for adjusting program volumes levels.
Thanks for the KDE developer(s) work for helping get OSS back into KDE 4.
