From a user report to customer support.
You have two separate external controllers, such as a Korg nano-pad and nano-controller, and you'd like to use both of them to control the KARMA M3 Software or KARMA M50 software. But the KARMA Software only has one port available to be assigned to RT Control in the Preferences > RT Controls section. And the nano devices do not have traditional MIDI outs, so they cannot be plugged into a hardware MIDI merger - they connect directly to the computer via USB.
Download and install the free MIDI Yoke and MIDI OX software. These are software MIDI routers for the PC that can perform merging from two separate sources (i.e. two nano devices) and send them to the single port that KARMA M3/M50 has available for RT Control.
MIDI Yoke and MIDI OX are easy to configure. MIDI OX must be loaded before starting KARMA M3/M50, but it works now perfect with both KORG nano controllers to control all parameters of KARMA M3/M50. All details are in the diagram (click to open large version).
Mac OS X Procedure
Download and install the free MIDI Patchbay software. This is a software MIDI router for Mac OS X that can perform merging from multiple sources (i.e. two nano devices) and send them to the single port that KARMA M3/M50 has available for RT Control.
MIDI Patchbay is easy to configure. Simply choose "Edit Virtual Outputs.." from the MIDI Outputs: pop-up menu and create a new virtual output (ie KARMA RTC in the example image). Then assign that output to each of the nano devices in the patch. The patchbay document, and its associated virtual outputs, should be saved and MIDI Patchbay should be running with this document open before starting KARMA M50, but it works perfectly with multiple KORG nano controllers to control all parameters of KARMA M3/M50. All details are in the diagram below.