need help playing midi files online

[TJMac]

There are a few sites that are for musicians that have midi lessons. Years ago I was able to play them with a firefox plugin (streaming), but recently I've spent hours trying to get it to work with my current system... and I'm out of ideas of what to do. Can someone help?
I am running KXStudio (Kubuntu) 10.04 64-bit and Firefox 3.6.11.

[zwenny]

Is a midi sequencer installed? timidity / playmidi or something similar and
did you try this: http://tech.yanto-flora.net/e-071020-014418_Playing_Midi_Files_in_Linux_Firefox?