Several people have complained about midi not working in Knoppix. I got mine working on a HD install and I thought I would post how I did it for those interested.

For my sound I am using the Intel 810 + AC97 onboard audio.

I'm sure there is a command line way to do this but I just did it in the KDE control center.

Go into the control center.

Go to "Sound"

Go to "Sound Server"

Click on "Start aRts sound server on KDE startup"

Click apply down at the bottom.

A message will pop up asking if you want to restart the sound server. Click "Yes".

You should be able to play midi files with Kmidi.

I was advised that doing this would fix a problem that I was having with low bit rate mp3's playing at high speed and sounding like the chipmunks. The bad news is that this didn't really work because Knoppix doesn't include the xmmsarts plugin and when I try and grab it, apt-get tries to uninstall 20 packages. I don't want to do that, but the upshot is that by enabling aRts you should be able to play midi files. It worked for me at least.