Get two professional guitar players in a room and ask them, “What's your most important piece of gear?” You’ll almost certainly get two different answers.

Is it the pickup configuration? The specific tube type in their amplifiers? We don't know, and they don't always know, either. The world of guitar tone is almost as driven by myths and snake oil as ancient Greece itself. Every guitarist prays to different gear gods, and every city-state of nerddom is convinced it is right. 

But what if you actually want to listen for yourself and decide what matters, using A/B listening tests? It's really, really hard to find volume-matched comparisons. That’s why I have become obsessed with Nashville, Tennessee–based YouTuber-guitarist Jim Lill. In a Mythbusters-esque series that Lill calls Tested, the session guitarist and songwriter brings your ears and eyes along on his personal journey. He compares various components of the electric guitar and its many amps and speaker cabinets, aiming to determine what makes the biggest difference in sound.

For a gear nerd with my own small hoard of guitars, the results have proven nothing short of astonishing. I’m not exaggerating when I say that Lill’s videos have fundamentally changed how I think about how guitar tones are made and how to achieve them.

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Lill's audio tests are based on a simple concept that would've been impossible just a few decades ago. You certainly can't do it live—even with the speed and soldering skills of a modern Fender Custom Shop employee, it’s hard to, say, swap two pickups back to back and not lose your sense impression between listens. Back when Lill's heroes were recording songs, you would've needed an ADAT machine or a very high-end tape machine.