Music enthusiasts will tell you there's nothing quite like "tube sound", the warm, rich sound quality that old vacuum tube amplifiers bring to the music played through them. And they'll pay top dollar for it! Once considered obsolete, vintage vacuum tube amps now sell at a premium, because audiophiles want to reproduce the harmonic distortions this old tech is so famous for.
This now-beloved distortion was initially seen as a bug, not a feature. It was an unintentional byproduct of the technology used at the time, an artifact of how vacuum tubes work rather than a premeditated characteristic of the hardware design. Later, we developed transistor amps, which have a "pure" sound that eliminated those distortions. Only once those transistor amps came onto the scene did audiophiles begin to reminisce about "tube sound". In fixing the flaws of the old paradigm, the new design brought to light that some of those flaws—like tube sound—were actually quite enjoyable.

A vacuum tube amplifier (a.k.a. valve amp)

A transistor amp (a.k.a. solid-state amp)
Technical constraints can give rise to incidental but delightful flaws, beyond just "tube sound". Embracing these euphonic distortions is a common way people relate to and embrace outdated tech. CRT televisions, 8-bit pixel art, and sepia photography all have enthusiasts who adore these once-ubiquitous technologies. We've now surpassed the technical limits of those old mediums, but these aficionados savor precisely the aesthetics produced those old constraints that have been "solved" by newer tech. They take inspiration from those aesthetics and recreate them with new technology.

Pixel art is thriving in our 1280x1024-resolution world. Delightfully, this gif also shows off our contemporary taste for CRT-style scan lines, too. Two-for-one!

Example of the famous CRT scan line effect deliberately applied to an image.

Sepia is a popular tag on instagram.

These old, flawed mediums are nostalgia machines, and that's a big part of the draw. You don't have to be a CRT television connoisseur to appreciate their distinct aesthetic. Their crackly flicker, scan lines, and magnetic damage make each of these TVs a time machine, teleporting you back to an earlier era.

Euphonic distortion, in the purest sense, is a product of is time. In a way these distortions are most "authentic" artifacts of a given era. No one planned for them, and only after removing these random errors do we appreciate the value they added. Their lack of self-consciousness is disarming. Euphonic distortion is authentic because it's not something you'd come up with; it simply arises as a function of the technical constraints of a particular moment.

But it's not just about nostalgia. The constraints imposed by an old technology can also produce joy in their own right. For example, stick-shift cars make you feel one with the vehicle in a way an automatic transmission cannot. The extra complexity to shift gears in manual transmission cars is exactly why most American consumers abandoned them for automatic... and it's exactly what draws enthusiasts back to manual cars. What was once a function of circumstance is now a conscious choice.

Of course this "vacuum tube nostalgia" is not the fate of every historical glitch. Few accidental artifacts are beloved. Many more are abandoned as fast as we come up with a better way, something that overcomes that a limitation. For example, screen burn-in is a phenomenon of phosphorus-based monitors that happens when a specific image literally burns the inside of the screen over a prolonged period. I find it hard to imagine that anyone would want that effect. You're never going to get a burn-in filter on Instagram. It just looks dirty and gross, and makes it hard to see other images on the screen later. Most flaws go the way of burn-in. Very few are actually charming or nostalgic; most are simply worse than the new and improved ways of doing things, and we abandoned those practices for good reason.

Burn-in just doesn't look good. We're not going to get a burn-in filter on Instagram any time soon.

Even those few historical glitches that are beloved work well in some contexts but not in others. While I adore the aesthetic of 8-bit pixel art, I wouldn't want to live in the world of the 1980s, when digital artists were so constrained in their expression. The inflexibility of their medium gave rise to a beautiful, distinctive art style, but it also inhibited the range of aesthetic experiences they could create.

As much as I love 8-bit art, I'm glad digital artists like Dan Luvisi are no longer constrained by a narrow pixel palette for all of their work.
We can have the best of both worlds: digital artists now have a far more varied palette to choose from as they create art, but they can also go back to the old constraints of pixel art when seeking that particular style. Their toolset is all the richer for having gone through a period of arbitrary, unintended technical constraints, because 8-bit art is a style they may not have realized was possible or desirable if they hadn't at one point had the constraints.

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1 – There's now a thriving market for this obsolete amplifier technology, for the precise reasons that once made it outdated and uncompetitive. These amps are pricey, especially original vintage ones. If you don't want to spend thousands of dollars on your own tube amp, you can add artificial distortions through a special feature of many modern amps or in the post-processing step of an audio-editing tool. Many modern songs use this aesthetic in intros or as a trick to set the scene and set a particular aesthetic and time, and even recording studios that work in an all-digital medium use tube pre-amplifiers inside of microphones.
2 – I'm not an expert on any of this! Most of what I know here is from conversations with old musician friends and casual research. Please correct/add to this if you know more.