I installed Nulloy sound player , from the respository , and it needed plugins so i installed Gstreamer
Now i tried to open a midi file and it says GStreamer is missing a plugin ??
Whats the name of the GStreamer midi plugin ??
generally speaking you’d need gstreamer from the packman repo for working multimedia
do you have the packman repo?
have you done a full vendor change to the packman repo?
although the crippled version should work with midi files
tell us your repo list
zypper lr -d
Although I’d be surprised that you saw an error about a midi plugin, in general you should be implementing everything multimedia-related using packages from the Packman repo.
If you haven’t done so, visit the Multimedia Forum and read the stickies following links and instructions how to install codecs, add the Packman repo and implement a Vendor change to that repo.
TSU
Codec’s are always available here 
or at least have been for a very long time. One click and no need to worry about what might be imported from pakcman if some one isn’t too clear about precise zypper commands.
http://opensuse-community.org/
Also specific nvidia and amd drivers of late. That can save guessing which one to use.
John
for midi support you might need to have fluidsynth and fluid-soundfont installed
zypper in fluidsynth fluid-soundfont