I know that in the past most of you have recommended updating knob and tube wiring with Romex cable. But why bother replacing it? Embrace it. Take advantage of its presence and use it to run your new wires. Don’t know how? These pictures give you a simple and practical technique. 
:mrgreen:
At least if they were soldered the Electrician did not leave any evidence for you know who. LOL
At one time that type of connection was an acceptable method for K&T. Often called a western union and as of about 15 years ago still taught at the electricians union.