The Core wire is what is usually what the magnet/coil pickup picks ,er, up. and many alloys in addition to bronze are not magnetizable , but are used to effect increasing the mass of the string, and thus the way it vibrates across the magnetic field.
nickle plated steel windings , certainly, but nickle and monel and some stainless alloys contain no iron , but they add mass and thus vibrate at an appropriate tension for the pitch needed.
I stuck some of the loops over some recycled guitar balls and use 2 strings on each ball on the thru body type ferrules on my 8 string FM61se, EMG pickup, ghs a250 bronze strings. plenty of output of g and d , a level similar to the other ones..
when i change them , maybe something different , next time, , in the meantime its good enuff..
writing about music
is like dancing,