In certain windowmanagers (Ion, wmii) Renoise takes keyboard focus completely and I can’t change between applications via keyboard (like with alt-tab). Also in Gnome and Fluxbox Renoise is minimized when I use alt-tab.
I’m running rn in gnome. There is a keybinding in rn for alt+tab you can modify so it doesn’t minimize rn; or do anything at all if that is your wish.
This behavior is intended, in the past beta’s you could not switch apps at all when Renoise was focussed.
There were problems to get this application switching fixed and some sort of hack is applied to achieve this.
It is not really a neat compromise but switching somehow works.
The problem is that switching does not work at all in Ion or Wmii. In them I switch between application using the ‘windows-key’ (Mod4) + some other keys. IMO this should not be intended behaviour, because there should be no bindings in Renoise that utilize Mod4.
There is an option in Renoises Keyboard Preferences, to control if Renoise steals/overrides the WM shortcuts or not. Toggling this option should do the trick for you.
We had to add this option, because a lot of shortcuts conflict with for example Gnomes keyboard set…
Ahh great. I was just being blind then… Luckily whining helped. Thanks. Also I was initially wondering whether I should post this in Help & Support or Bug reports.
If you have turned of renoise taking control…
In Gnome (well on ubuntu anyhow)
Click on System > Preferences > Keyboard Shortcuts.
You can come up with numourous non-conflicting keyboard shortcuts. I think you have to re-login for changes to take effect.
But on the subject of switching tasks in linux…
http://wiki.awn-project.org/Main_Page
Its a rather fancy see through task switching tool bar.
Thanks, I was about to abandon when I read this!!! 
I think I can now think seriously about buying Renoise.