Just a thought....have you checked to see if the "driver" module(s) are being loaded? I have an older PCI128 card here that uses the es1370 chipset, and it works fine in Linux. A "lsmod" command should show both a "soundcore" and a "es1371" module loaded. If they are not there, you might want to use MODCONF and add at least the es1371 module. It think it will drag the other one along with it at boot-time.
BTW, if you EVER get this card to play MIDI files under Linux other than by using timidity, PLEASE let me know how you did it!! I have been searching for over a year! The Commercial OSS "drivers" work fine with this card too... Cheers, -Don Spoon-