Quick Question on MIDI Signal Behavior

Midi clock signal? MIDI-OX software might be helpful to investigate

More information required about the controller you are using.  Some of them send a continuous handshake type message.  It is not an issue really.  It is more than likely the Active Sense message:
 
Active Sense:  OxFE
 
An optional "keep alive" message that, when implemented, can be used to detect if a transmitter has been accidentally unplugged. A transmitter sends them every 300 milliseconds. If the messages stop flowing, the recipient times out, and cleans up by stopping sequences and turning off notes that would otherwise be stuck on.
 
Other controllers don't do this so you must have one that is sending that message. My Kurzweil PC3K for example does not. You may be able to set that not sure. But is usual for some controllers to do it and others to not.
 
Just don't look out the corner of your eye and concentrate on doing the parts instead!
 
I doubt it is a midi clock. Controllers don't often send it unless it is more of a workstation type controller and in most cases it defaults to off and you have to tell it to send. Midi clocks are ore often coming from your DAW to receiving devices that can utilise them and sync to them.
 

Did you try recording it and checking the events to see what they are?

The RME could be indicating a number of things, none of which are problematic.

Firstly, MIDI clock, Active Sense, Start/Stop/Continue/Song Position Pointer messages that are sent when Sonar’s sequencer engine enters play mode don’t get recorded to tracks. They are however important for keeping MIDI-controlled stuff synchronised. I don’t think the RME will indicate any of those, at least I don’t remember seeing mine ever do it. MIDI sync/clock and what Sonar does with it is a per-project preferences setting. All that stuff is somewhere between essential and harmless depending on your MIDI hardware setup.

What might be happening is that MIDI data is being sent to the RME because it’s being sent out of Sonar on all ports. The RME will indicate it’s receiving MIDI, though only the stuff set to the right channel will respond to it. What the LEDs do confirm is that you’re enabled the RME MIDI ports in Sonar’s preferences.

MIDIoX is a really useful - essential if you have MIDI hardware - free application that will show you what’s being sent to what. It’s usually a good idea with any MIDI analysing tool to tell it to not show you Active Sense and clock messages as they can fill the screen pretty quickly. Unless that’s what you are looking for, of course.

With most things MIDI, if it works then it’s often best left alone. The clock and sense related date takes up so little bandwith they’re not worth worrying about even if you have no MIDI hardware.