Sooreaver1997

I think the problem is that the standalone synth is not a VST, so Sonar won't recognize it in the plugin directory. You need to make sure you download the VSTi (a .dll file) and put it in the VST folder that Sonar is scanning. Also, the unofficial classic VST you mentioned works fine with DAWs like Sonar, so you can try downloading and installing that. Remember to re-run the rescan command in Sonar to make sure it updates the plugin list.