1. Place the plugin on the Master MIDI bus (since it's a multi-channel Synth, you don't need multiple instances, just one)
2. Go to the track properties and assign:
* Channel
* Instrument Definition (Qtractor comes with the "Roland GS" standard pre-installed)
* Bank
* Program
Unless that particular plugin works in a specific way and the instruments are assigned in the plugin. Then you just need to assign the channel to the track, and the rest of the settings in the plugin.
1. Place the plugin on the Master MIDI bus (since it's a multi-channel Synth, you don't need multiple instances, just one)
2. Go to the track properties and assign:
* Channel
* Instrument Definition (Qtractor comes with the "Roland GS" standard pre-installed)
* Bank
* Program
Unless that particular plugin works in a specific way and the instruments are assigned in the plugin. Then you just need to assign the channel to the track, and the rest of the settings in the plugin.
PS:
In any case, I recommend https://x42-plugins.com/x42/x42-gmsynth, which is native to Linux and probably sounds better.
This one lacks an interface; assignments are made from the track properties, as I've indicated.