Tried esddsp and there seemed to be a lot a latency when playing Doom. :o( So I decided to get the latest ALSA source off of the Debian unstable site and build myself some new sound modules (0.9.8). Which led me to completely overhaul the sound set up on my system (incidentally there's a good article on this over at the Linux Orbit site, go to http://www.linuxorbit.com and look for "Installing and Configuring ALSA Sound Modules in Debian GNU/Linux HOWTO".)
Here's a question for the Debianites out there, I used make-kpkg module-image to create the .deb package to install the ALSA modules. I also wanted to get some specific ./configure options fed into the build. However the only way I could see to do this was to go to /usr/src/modules/alsa-driver/debian and edit the rules file. I'm sure there must be a more elegant way to do this. Anyone know what it is?
Upshot was the with the rebuilt sound modules and a 'properly' configured ALSA interface into OSS, Legacy Doom goes like the clappers!! :oD. Still no music though.
As is always the way with these things in trawling round various sites looking for answers I came across a GNU/Linux port of Legacy Doom that uses SDL and doesn't have separate processes for sound (i.e. doesn't write directly to /dev/dsp). More good news was that its available as a Debian package, and I can personally vouch for its playability (still no music though!).
OK, starter for 10, who can tell me what SDL means in this context? :o)