First and foremost, when i have these situations where i'd like to control 2 combis at the same time, most of the times i end up merging the 2 combinators. For that, just select the 2 combis, and combine them. The result is a single combi with all the devices. You have to do some additional mingling and if it isn't in one of the base combis, add a mixer and route the instruments accordingly, but imho, this is the best way to do it as it is a good solution for sequencing, CV or a live performance... And with all due respect to others, a way SIMPLER and future proof (just save the final combi for future uses) instead of having to save a complete project.
That being said... since for recording context you can merge 2 combinators, or simply copy/paste the midi data from a track to another, I'll assume this question is for a performing situation. For this, and if you really don't want to merge the combinators, I would use the External control and the advanced midi section in the hardware controller.
The advanced midi controller allows you to select a midi port from 4 different controllers and 16 different channels and route them to whatever track you want to send it. And the best part is that you can make 4:M routings, because you can assign 4 different banks to the same controller.
So for using the Advanced midi controller have to go to Preferences->Sync and define your midi controller as one of the mid bus sources in the Exernal control. In here, you just have to select the same controller for bank 1 and bank 2 (assuming you can't control what midi it is sending).
- preferences.JPG (30.97 KiB) Viewed 1276 times
Then on the rack you open the advanced midi control section in the hardware controller and select bank 1 channel 1 route it to the first combi,
- Bank 1.JPG (46.19 KiB) Viewed 1276 times
and then do the same for bank 2 channel 2 and route to the second combi.
- Bank 2.JPG (45.78 KiB) Viewed 1276 times
Now the first channel of your cotroller will be sending midi to 2 different tracks at the same time. However, the midi comming from the advanced controller is not recorded to the tracks even if you use it while record armed, so as i was saying in the begginning of the post this is a solution for performance situations.
If your controller can send multiple channels, and if it has a way to control zones, you can setup 2 zones in midi channel 1 and midi channel 2 and send the zones to bank 1 and just use channel 1 and 2 in the first bank.
The advanced midi section is usually forgotten functionality but an interesting feature to use reason with more "obscure" sequencers, or hardware sequencers, and in this case to use up to 4 devices and have more direct control and not being bound to the master control, surface lock, and normal midi behavior with 1->1 connections that are enough in a normal sequencing situation.
In live situations, what i used to do to have more control was having my main instruments as master controllers, and i had a second controller reouted to bank 1 and then have a bunch of different routings to 1-16 channels. This allows to have a bigger though stable project for a full gig with banked instruments mapped to keyboard zones and the 2 master controls could go up and down in the tracks dynamically.
Both these solutions are effective for mono or poly instruments too.
I hope this helps!