The Picturebook contains a Yamaha YMF-744B sound chip. This chip, while not supported by the current linux kernels, is supported commercially by OSS (available at http://www.openssound.com/).

The OSS drivers are not APM aware making them irritating to use with a linux-based laptop -- You don't turn it off, you suspend/sleep it.

ALSA supports the picturebook sound chip with it's latest drivers. You can grab them from http://www.alsa-project.org.

Once you've got them, you need to install them in this order: drivers, lib, utils. Note that you probably won't need to compile them again, probably just ./configure, and make install.

Then you need to edit your /etc/conf.modules or /etc/modules.conf (one is just an older name for the other... you probably won't have both). You should add something like the following lines:

alias char-major-116 snd
alias snd-card-0 snd-card-ymfpci
alias sound-slot-0 snd-card-0
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss 

The next part was weird for me... not sure what went wrong here, but I couldn't get my sound working without rebooting. In theory (i think), I should have been able to get away with simply running '/sbin/depmod -a'... hrm...