I am about to start trying to setup a midi/recording linux based system here myself perhaps we can share our findings? I will begin with apparently midi support isnt in the alsa-autoconfig that knoppix is using from what I can tell of course once hd installed it basiclly becomes debian anyway so I am thinking it can be added? I may be way off, midi may be being detected else where or even perhaps in that script but I dont think so? anyway in most of the better audio production linux kits I have looked at they seem to require (RT?) optimizations to the kernel anyway so a complete sound rebuild is probablly in my near future If however all your looking for is midi playback from applications like jazz I think they have a application that will allow you to route the midi to another application like timidity for play back just can't remeber what it was called may be -Jack- ? not sure ?
Hope this helps