Hi, first time posting here!
Some time ago, I built an arduino midi (usb) controler (using a Mega 2560) to control some parameters of my daw. That is working nice...
Now I recently got an nts-1 synth, and I want to figure out a way of controlling it using that midi controller and a midi-usb keyboard I have...
I want to make this synthesizer receive midi commands from both my midi usb keyboard and my arduino mega based midi controller. This without a computer (so I can play anywhere)...
Something like this:
At first my idea was to "connect my midi keyboard to the midi controller via usb" and then merge the midi data from the keys with the data from the sensed knobs of the controller. (then send all of this in a second usb midi into the nts)
(I searched how usb works and figured out this wouldn't work at all because there are only two devices and no host) lol
I know I could make this easily using 5pin midi (the "real midi")... The problem is that my keyboard is only usb! 
: so im a bit stuck on what to do now...