I recently installed UbuntuStudio 10.04 in preparation for some audio and graphics operations I would need to be performing soon. Normally, I would have stayed with my beloved Debian, but for sake of convenience , I decided to use UbuntuStudio and chose the 10.04 LTS edition.
I am very sensitve during certain times about when my system is under a load, so I normally shut off all services I do not need, like bluetooth, accessibility options and so forth. And having gotten very spoiled with my Debian OSS4 sounds, I decided PulseAudio had to go.
This post is mainly for myself so I can just copy/paste into a terminal, but if you find it helpful, so much the better
A lot of this information is available directly on the referenced websites, I am just condensing things down a bit.
Remove PulseAudio:
sudo apt-get purge pulseaudio gstreamer0.10-pulseaudio
Clean out Alsa
sudo /etc/init.d/alsa-utils stop
sudo apt-get remove alsa-base alsa-utils
Change the default sound server and select OSS from the list:
sudo dpkg-reconfigure linux-sound-base
Install some prerequisite packages:
sudo apt-get install binutils libgtk2.0-0 sed gcc libc6 build-essential linux-headers-`uname -r` gawk libtool libgtk2.0-dev libesd0 libsdl1.2debian-oss mercurial
Now it is time to REBOOT! Things tend to go awry if you do not reboot now.
Get the source code and build .deb package.
cd /opt
sudo hg clone http://opensound.hg.sourceforge.net:8000/hgroot/opensound/opensound oss-devel
cd ~/
mkdir oss42build
cd oss42build/
NO_WARNING_CHECKS=yes /opt/oss-devel/configure --enable-libsalsa=NO
make
sudo make deb
sudo dpkg -i oss*.deb
Get our system sounds working
sudo apt-get install libcanberra-gstreamer
Use the Multimedia Sytems Selector in “Preferences” and set Audio defaults to OSS

Multimedia Selection for OSS Sound System
Lastly, add a custom application launcher in the panel or a desktop launcher for our audio mixer
I prefer the panel
Right click on panel ->Add To Panel -> Custom Application Launcher -> Name : OSS Mixer, Command: ossxmix
Pick any icon you prefer.
I normally reboot again.
To test your sound system, open a terminal and type in
Be warned that the volume may be very loud, so be careful.
Thats it for now.
References:
Ubuntu Community Help: OpenSound
Open Sound website: Configuring Applications to use OSS4