For me, being able to listen to precisely the same music with the same bias to my left and right ears would be critical, so I would never want to test different cables for each channel. That is even more important given I am mainly a classical music listener - the first violins are traditionally left channel based and that is my "acid test" above all others - how a cable handles mass violins. Only if it passes that test am I going to judge it on anything else such as timing, imaging and the ability to convey the sense of the original performing space overall. Apart from anything else, I hear differently in each of my ears - not just because each ear has very slightly different sensitivity thresholds (measured via audiometry), but also the shape of my head and outer ear are very slightly different on each side and that makes a difference as well to the way I would perceive sound in a room.
But for me, there was was test conducted a few years ago now by a German audio magazine, where they used a large number of different interconnects in an analogue setup and recorded the analogue output digitally at 24/96. So they ended up with a large number of comparative 24/96 recordings, with the only variable in the setup being the analogue interconnect. They also made a "reference" recording using "jumpers" that were very thick solid copper from memory (as in the thickness of a pinkie finger and around one inch long).
After I listened to all those files, the sobering reality was how much even the top cables tested "lost out" compared to the straight jumpers. Nevertheless, I was able to rank the cables in the order I liked. Then came the cost - the one I liked the most (Wireworld Platinum Reference) was out of my price range, but the Wireworld Gold Reference wasn't (just). I took a punt and then ordered that cable from a dealer I have known for a decade and have been a regular customer. But I loved the cable. There was never any danger of me returning it. I still use it and never have any intention of swapping it for anything else (except a better Wireworld!).
But I have actually used the above technique (trying a cable in a system and recording the output digitally) for other types of cable too, such as mains (power) cables. Although it obviously will not give you an accurate "end result" in terms of how the cable will ultimately perform in a "target" system, it still does firstly convey the essence of a cable's character. But I also do this to facilitate the more fundamental ABX test. I will ABX the digital output recordings to make sure I really can tell a difference and I'm not suffering placebo or nocebo effects.
Mind you, I am "done" with cables now anyway simply because of the cost. Depending on how much degradation a cable brings to the table, the costs can be horrendous. As I say, I am a Wireworld fan because to me they take the least away from the music whilst still being relatively affordable high end products at the top of their range. But as we all know, you can spend as much on a cable as you might a car.
