'Nordic Stringing' originates from players and luthiers in Sweden in the 90's changing how the low courses are strung in octaves. I believe it was a collaboration between builder Christer Adin and mandola virtuoso Ale Moller at first but has become a well known alternative.
Basically it uses a classical silver-plated nylon bass paired with a thinner, octave string in phosphor bronze, as seen in the photos. The result is a softer sound, less resounding and brassy, and maybe with a quicker note decay.
It is quite nice on the low 5th course of a cittern, or any of the low courses on the bouzoukis, OMs and mandolas.
Sometimes I can use ball-end classical strings which thread easily through the tailpiece string holes. Other times, the string can only be tied onto the tailpiece in the same way classical guitarists install their strings on the tie block.
Have a listen to the audio files and check out the video demos below to learn more.