Sound Flavour
Bernard you should try making your interconnects totally non directional by making them in star star quad configuration, and the conductors as they come off the reel connecting active from the source to the load and back again, and the same for the neutral (or - phase) conductor.
If you twist this assembly carefully and preserve star quad configuration over the length of the cable, I am sure that you will notice a nice difference.
Years ago I had this setup between my cdp and power amp that were in fixed positions, and this allowed me to use exact length interconnect wires (1mm diameter 6 nines purity copper with silver plating) soldered directly to the plugs sticking out the back of them.
The wires were diagonally about 4mm apart.
I tried a polyethylene filler rod down the middle and wrapped with white teflon plumbers tape or standard office sticky tape, with and without thin teflon insulation sleeves (of 2 different colours) on each of the 4 conductors per channel, and with all conductors in either direction.
I found the 3 teflons to impart a definite sound character, as did the cellotape.
The best however was without any filler rod and the 4 bare wires placed in space in the direction cancelling and star quad arrangement.
After fitting and experimenting with these interconnects is when this system really came to life and gave fantastic depth imaging, and even sounds from behind.
I did not try the experiment of closely twisting the wires (because I did not like the sounds of the insulations/dielectrics), but I expect this should work nicely with your thin enamelled wires, but in your case you will be at least doubling shunt capacitance and halfing series resistance, and a lessening of series inductance.
This in itself will likely change line level source to load characteristics, but this may be a good experiment for your self to guage wire directional characteristic or not, and open the mind.
Harry, I think the effects you describe are more than mechanical stiffness.
I have found different sounds with different coloured otherwise same tubings - this is an effect due to change in dielectric properties due to differing pigmenting materials I am sure.
Black plastics commonly contain a cadmium compound, white commonly titanium compound - red I dunno.
I do know that I won't drink out of black plastic or porcelain though.
Regards, Eric.