[LAU] Qtractor and soft synths

I am running Ubuntu 18.04, with Qtractor 0.8.5 I have some midi files (generated by Lilypond), which I should like to edit and improve in Qtractor. In Qtractor I can play the tracks through Timidity. The Track dialogue offers me sounds from the FLuidR3_GM soundfont and also soundbank-emg. But these sound identical, and I think only FluidR3_GM is being used, which I have set as the default in Timidity. I would like to use other sound fonts (e.g. Virtual-Playing- Orchestra3), but I have never worked out how to achieve this. For instance, I have installed WhySynth (using apt), and after much trial and error I managed to get it to appear as a plugin in the Track dialog. I clicked on "Add", and WhySynth then appeared as an additional option under "MIDI/Instrument". But after selecting a WhySynth sound, I still hear the FluidR3-GM sound. This is presumably because I haven't connected WhySynth and Qtractor in the Connections window (or QJackCtl's Connect window), but WhySynth doesn't show up there at all. What do I need to do get Qtractor to use sounds from WhySynth? David