Hey guys,
I want to MasterSystem compose music with Deflemask, but there are only a very view instruments to take. Any idea how to get
instruments (any package to downlaod online)? I also don't know whether you can create them. Only can change the sound of a 
current instrument, but cannot create new instruments. 

Heyo friend! If you want to download some vst there's a good website called rutracker, where you can download them via Torrent links. It's a russian site but you can translate it automatically. I got mostly all of my VST there. 

For creating them, well you can "modify" via oscillators and waves like Vital or Spectrasonics, but those are VST you have to download too. 

If you want to contact me concerning the type of libraries and vst you want, don't hesitate!