Hi again and thanks for your answers!
The reason I was asking these question is that I was running Ubuntu Studio on my Computer and couldn't get almost anything to work. On another partition, I used (and still use) Linux Mint 8, which runs nicely, but isn't really tuned for audio, and I didn't really want to risk to spoil my system by installing rt-kernels. Yesterday evening I finally replaced Ubuntu Studio by AVLinux 4, and: up to now it seems to run perfectly fine.
That was a huge surprise for me, cause Ubuntu Studio really got me mad. Since I shared the idea, that Ubuntu should be the easiest way to go because it's "Ubuntu", and it has reputation of being extremely "n00b-friendly", I started thinking that configuring Linux to work with audio requires (at least) mad geek skills.
First of all, with the fresh "studio" install I didn't have any network-manager running and I couldn't install it from dvd, since apt somehow wouldn't accept the studio dvd as a repository. So I had to pass a cable through the entire flat to access the internet, download network-manager to use my wifi connection. Then, Studio was extremely resource hungry. Although I replaced the desktop by "xubuntu", it still ate up over 50% of my (512 MB) RAM just after the boot. Okay, maybe I should buy more RAM to use the latest stuff, but I've been running some old audio applications under M$ XP without ever feeling the need of it. Then, half of the huge list of applications in the "audio" folder didn't even think of running. I couldn't get jack to work. I couldn't get the timidity-daemon to work properly (except once, but after reboot it ceased again), although I tried really hard. I suspected that all these complications might have been caused by "pulseaudio", but trying to de-install it via synaptic (as the Ubuntu-wiki explains) just resulted in having no audio at all, so I reinstalled it. Trying to install "Impro-Visor" was complicated by first having to install Sun Java. Well then, it was all in vain, because the midi-output via timidity-daemon didn't work. And so on, and so on....
So then, after seeing some people recommending "AVLinux" on this forum I decided to try my luck with it. Basically, I was expecting nothing, since it is a very small project and it didn't claim anywhere to be extremely newbie-friendly or whatever, so it must be even harder to make it work. However, I read that it runs without pulse-audio, so I hoped the audio-system could be easier to understand, and uses LXDE, being a bit lighter on resources. I decided to give it a try.
What I got is really amazing. It immediately recognised my wifi card and I could connect to the internet. It takes only about half the memory Ubuntu studio took, even with the xubuntu desktop, so I think audio applications should run fine without having to buy new ram. Jack runs immediately. The menu is well organised and all applications in there seem to run, look nice and tempting. Media-codecs and Sun Java are pre-installed (okay, that might be kind of an ideological question and I know how to install it by myself, but it makes it much more usable out of the box). The best media players (Exaile, VLC) are pre-installed. Wow! Many thanks to the developer(s) (?) of this splendid distribution! You absolutely saved my linux-audio-live!