I've been happily using the latest version of Sonar Pro with my (original) m-audio m-track (midi 1x1, 2 audio) interface via usb.   I'm running windows 7 pro SP1 (64bit), fully updated.   All was working well with the m-track drivers installed (dated 2013 if I recall).
 
I then tried to connect my Yamaha MX61 to the same system via USB (in addition to the m-track).  With no additional drivers installed, Sonar did not recognize or give me digital audio device options.   I then installed the Steinberg drivers from the Yamaha website.  Once this was done, Sonar saw the keyboard as both an audio and a midi device, but the m-track audio INPUT disappeared and I was unable to select the Yamaha audio as input as it was greyed out (so effectively no audio inputs).   On the output side, only the Yamaha was selectable (m-track was visible, but greyed out).
 
Can someone point me in the right direction regarding getting the m-track and the mx61 to coexist nicely under Sonar?  Thanks in advance.
 
 

With ASIO, you can only use 1 device at a time. I suggest connecting the MX61 to the M-Track with MIDI cables and just use the M-Track.
In SONAR's Preferences, ensure the M-Track is the only device selected for audio and MIDI.

57Gregy
With ASIO, you can only use 1 device driver at a time

fixed