I'm using Gentoo linux 1.4, and I don't have any sound in Vendetta. Other apps (quake3, xmms, etc.) work. The volume is not muted ;).
I have only the following error in the console:
/dev/dsp: input/output error.
Alsa-oss is installed.

TIA for any ideas!

Well, fixed...
I had to use the game like Quake3: start 'artsd', and than artsdsp -m vendetta.

I use this to start up vendetta:

#!/bin/sh
xgamma -q -gamma 2.0
sudo su root -c 'echo "vendetta 0 0 direct" > /proc/asound/card0/pcm0p/oss'
sudo su root -c 'echo "vendetta 0 0 disable" > /proc/asound/card0/pcm0c/oss'
amixer sset PCM,0 28
/usr/local/bin/vendetta
xgamma -q -gamma 1.5
amixer sset PCM,0 24

The two key lines are the two sudo lines.

Hmmm, you shouldn't have to start artsd... As a matter of fact, the arts daemon detracts from the performance of vendetta. Have you done the following:

"emerge alsa-lib"
"emerge alsa-driver"
"emerge alsa-oss"
"emerge alsa-utils"
"emerge alsa-tools"

?

Also, make sure that your kernel config for sound is proper. I would tell you mine, but I'm compiling it yet again, and cannot spare the time. :)

PPS: If you got a nvidia card, turn on FSAA and DigitalVibrance for Vendetta. It looks pluscool.

sessionID: artsdsp -m vendetta works perfectly ok ...you don't have to restart artsd ...thx for the tip though

Evil me still has an old Esoniq Audiopci '97 :), so I don't even need alsa to use sound. All I do is compile it in the kernel, so neener neener neener!

Which means you have OSS. ALSA works better, you know... And OSS is depricated in 2.6, in which ALSA is default. So neener neener neener.