Instrument Cable Tone

I downloaded a blind study of many different cables in a line level application years ago. All kinds of subjective claims were made that added up to nothing more than complete randomness. My guess is there may have been some slight differences in noise signature due to shielding variances. People can often prefer some low level noise in a signal -- perhaps closer to our experience in nature: wind through trees, rustling leaves, rain, etc. Other than durability, proper shielding, static and handling noise rejection, the two factors worth considering for passive Hi-Z applications are capacitance (parallel) and velocity. The velocity value is really never offered, so forget about it. Steel core cable is higher velocity than Copper, but it's not really an issue with passive Hi-Z guitar signals.

OTOH, I've done tests with my 19pF/foot cable where I could hear a significant difference in the high end after cutting just a few feet off. Whether you'll hear a difference depends on the pickup specs and coil integrity. I still think the 25pF/foot Rapco 'G1' series cable is the best BFB. Replace the plugs with something more sturdy if needed. The 19pF/foot George L solderless cable is Steel core, if you are so inclined.

Such a loaded question!

Simple answer: anything above mid-level cables ... and with them being no longer than about 20-feet ... you'll never hear the difference between any two given cables. Now for the long answer ...

It is well documented truth that Stevie Ray always used the "cheap grey curly cables from Radio Shack" when recording ... and was practically on a one-man crusade AGAINST the first wave of "hi-def" cables coming out in the late 80's/early 90's. Basically, he was COUNTING on the top-end loss of the cable as part of his tone, and felt the amps sounded harsh with high-dollar cables ... and his point was totally valid.

Likewise, Ken Fisher (Trainwreck) almost always included speaker cables voiced to his heads ... often very long, low quality cables ... he looked at the speaker cable literally as part of the output stage of the amp ... where most amp designers simply try to eliminate the speaker cable's influence as much as possible by using big short cables!

Personally, I've been a part of dozens of guitar cable listening comparison tests (many at the invite and expense of the companies manufacturing high dollar cables). Here is my take:

The only real audible difference to be found is at the extreme bottom end of the scale. The totally cheapest, longest cables will most definitely loose a notable amount of top-end, and a little overall signal level, too ... a nice way to tame an overly aggressive/bright amp!
On the other side of the coin would be any cable that's of "decent quality" and not longer than say 20 to 25-feet. In that world they pretty much all sound the same ... and have the same distinguishing feature: the longer the cable, the more top-end loss will occur. The reason is so simple that I always teach it on day one of my in-studio audio classes at Vol State:
A guitar pickup is a very low-level and high impedance transducer, and a guitar cable is an un-balanced conductor ... meaning the negative signal is actually carried ON the shield, not indipendantly. The result: with every millimeter traveled down the cable, more of the low-hanging electrons are stripped away ... that would be the delicate high-frequencies. Generally if you have a mid-level or better cable of 20-feet or less, there will not be enough of a difference to cause you to actually notice the loss ... but ... let's say you have a typical pedal-board setup of ...oh, twenty feet of cable from the guitar to the pedal-board, and then 20 more feet to your amp ... well now you are getting to the level of possibly being able to hear the loss. The easy fix is simply to have one pedal (preferably the first) be a "buffer", which will in essence turn your signal into a low(er) impedance signal that's not so prone to degradation. But ... that's a topic for a blog in itself.

Some great links to continue this exploration:
https://wgsusa.com/gods-tone
https://www.guitarplayer.com/miscellaneous/5-things-about-guitar-cables
https://www.thegearpage.net/board/index.php?threads/srvs-fave-guitar-cab...

Absolutely Vaughn, a very high capacitance cable can put your pickup resonance peak in the sweet sounding zone (normally in the 1.5~2kHz range) depending on a few factors. Jimi Hendrix's long (50'?) coil cable he used on stage measured ~2.4nF. That's more than 10x the capacitance of my 8' ~160pF BL-150 cable ( also Steel core from Wilde pickups)! Of course, the Dallas FF or Vox wah pedals he plugged into both had such a low ~70k Ohm input impedance that his ~2.4H Strat pickup resonance was almost completely damped down (to ~2dB by my calculations), and the dynamic range affected (a key part of the Fuzz Face sound). It's worth considering the tip to sleeve capacitance value of any cable regardless of length. Some expensive cables may have as much as ~3x the pF/foot value of the cheap old Rapco G1 series.