Hello Jens,
you should first check, if your joystick is supported by linux. I find
the "jstest" program useful to determine if all axes, buttons of the
joystick are working. If you don't have it you could try building your
own:
http://packages.debian.org/stable/utils/joystick
Note that you may require a kernel module for your joystick, which may
not be compiled/installed yet.
If your joystick is working you can try aseqjoy to map it to an alsa
midi controller:
http://www.terminatorx.cx/aseqjoy.html
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