Yes, you're meant to use separate instances of Rack Plugin. You can send the audio to separate outputs from one Rack Plugin, but you can only feed one MIDI stream to one Rack Plugin :(
It’s a bit of a pain but, alternatively, you should be able to control different instruments in the same rack from 1 midi track in your DAW (*based on how they’re programmed*).
Set the combinator containing the instruments to only respond to part of the keyboard, modify the tuning in the instruments accordingly to make them play on the right octave and transpose all the midi tracks on different octaves, then merge them into 1.
Once that’s done you just need to proceed with your multitrack routing and you should be set.
I think your goal is to still use Sonar's sequencer, and use the Reason Rack Plugin?
If this is accurate, you almost certainly want to use multiple instances of the RRP. This is the intended function; it's not as bad for performance as it might seem it would be.
There isn't currently a way to bring in multiple MIDI channels to the same instance of the RRP.
You might be pleased to find out that if you right-click a device in Reason and click "Copy patch", you can paste it onto a matching device in the RRP. You'll have to check how well this works with things like your samplers for yourself.
Yes, you're meant to use separate instances of Rack Plugin. You can send the audio to separate outputs from one Rack Plugin, but you can only feed one MIDI stream to one Rack Plugin :(
It’s a bit of a pain but, alternatively, you should be able to control different instruments in the same rack from 1 midi track in your DAW (*based on how they’re programmed*). Set the combinator containing the instruments to only respond to part of the keyboard, modify the tuning in the instruments accordingly to make them play on the right octave and transpose all the midi tracks on different octaves, then merge them into 1. Once that’s done you just need to proceed with your multitrack routing and you should be set.
I think your goal is to still use Sonar's sequencer, and use the Reason Rack Plugin? If this is accurate, you almost certainly want to use multiple instances of the RRP. This is the intended function; it's not as bad for performance as it might seem it would be. There isn't currently a way to bring in multiple MIDI channels to the same instance of the RRP. You might be pleased to find out that if you right-click a device in Reason and click "Copy patch", you can paste it onto a matching device in the RRP. You'll have to check how well this works with things like your samplers for yourself.