Last month, we profiled a rock of the DJ booth, a humble platter that's gone more or less unchanged for decades. The Technics SL-1200 wasn't just a DJ tool, but the tool that defined mixing as we know it. The gestures and manipulations through which DJs interact with music—cueing, scratching, speeding up and slowing down—were invented on it. And whether you got your first pair in 1983 or 2013, you'll play them in the same way.

But almost as soon as Technics took up their long residency in clubs far and wide, the situation on the ground began to change. At the dawn of DJing, vinyl wasn't just the preferred format but the only format for mass-produced recorded music. Over the last three decades, though, we've had a series of shifts—first came the CD, later the internet and mp3s. With computers, we also witnessed a profound democratization in music production, one that flipped the script on where, how and how quickly music could be made. None of this unseated the 1200 as a profoundly important tool to DJs; it did, however, mean DJs had needs that Technics decks alone couldn't accommodate. Introduced in 1994, the Pioneer CDJ came to represent a different sort of stability in the booth—where 1200s would ensure DJing could always stay the same, CDJs reliably evolved with the times.

It's a curious twist of fate that as direct-drive turntable design was reaching its late '70s apex, technology was moving in a vastly different direction. The Philips Corporation, who'd been working on optical storage since the 1960s, went public with their technique in 1972, the same year Matsushita released the original Technics SL-1200. And as the MK2 deck was arriving in shops in 1979, Philips was joining forces with Sony, who had developed the error-correction methods that would make optical storage accurate and reliable.

A number of Japanese electronics makers, Matsushita and Pioneer among them, were working on prototypes for optical discs and players. But it was Philips and Sony who would hammer out the spec (known in the industry as the Red Book) that standardized the disc itself, the format of the digital information imprinted on it and the error correction used in decoding. By October 1982 in Europe and Japan, and March 1983 in the United States, as turntable-led hip-hop was spilling out of the Bronx and starting a lengthy pop-culture moment for the 1200, the first CDs and players were arriving in shops.

How records work is pretty easy to understand—the needle follows the record groove, which is an analog of the waveform of the sounds it contains. That you can see the grooves and the whole process playing out in the open demystifies things further. What happens when you slide a CD into a player, though, has always been more mysterious. The "groove" is actually a series of a few billion depressions, or "pits," on a metalized surface sitting just under the label of a CD. When a laser inside a CD player runs over the groove, it reads the pits and the spaces between them ("lands") as differences in the intensity of the reflected beam. These differences correspond to the ones and zeroes of digital information (corralled into "frames," the informational building blocks of CDs), which the player decodes into the sound you hear coming through your speakers. Error correction is robust, enough so that an expert once told me half-seriously that you could shoot a hole through a CD without noticing a difference in playback. But any pickup system dealing in lasers and nanometers—and without a physical connection between that pickup and the surface it's reading—is going to require some hefty mechanical accuracy. That's one thing in a living-room hi-fi system, but quite another in the sub-bass-flooded confines of a nightclub.

We asked Pioneer to name some of the biggest changes they've introduced to CDJs since they first appeared in the mid-'90s. Simon Hart, an executive for Pioneer in Europe, counted them down.

Vinyl emulation
This was the big one that began the adoption of the CDJ as a legitimate DJ turntable and credible alternative to the analog turntable.

Quantize
Perfect accurate looping on the fly became possible thanks to a quantize feature that read track waveforms in rekordbox and snapped beats to the grid with millisecond accuracy.

Sync
While on the surface it might seem like a contradiction to the art of DJing, in practice it's a powerful creative tool for multi-layering—something software DJs were already used to.

SD/USB sources
The end of lengthy CD burning preparation. DJs can now obtain instant waveforms, track data and accurate BPM readings by exporting from rekordbox to a drive or card.

rekordbox
Our music management preparation software brings the CDJ-2000 to life. It has its own app and offers wireless play from tablet to CDJ over its own wireless network.

Pro DJ Link
By network-linking the CDJ900, CDJ-2000 or CDJ-2000nexus, DJs can play across four decks from a single source. The "live" deck jog wheel turns red, and fast, hassle-free DJ changeovers are possible.

It's not surprising, then, that the CDJ's roots trace to another unforgiving environment: the car. "After achieving a number-one position in the car audio market with our anti-vibration CD technologies in the early '90s, we looked for new areas to harness our digital competencies," says Simon Hart, Pioneer Europe's senior marketing communications executive. Engineering a CD player that could withstand playback in a patently impure environment, though, was just one design consideration among many. Since the beginning, CD players could play, pause, fast-forward/rewind and skip from track to track, but this didn't begin to qualify as DJ functionality like playing vinyl on Technics.

Pioneer's attempt to address the shortcomings of existing players from a DJ's perspective was 1994's CDJ-500. (It's been claimed elsewhere that a model called the CDJ-300 came first, in 1992, but as far as Pioneer is concerned, the 500 is the beginning of the line.) The deck was cutely clunky in a similar way to early mobile phones—you loaded CDs under a pop-up door on the front panel, just as you would on a boombox from the same era. All that aside, the CDJ-500 had acceptably fast starts and stops, and it could cue (by way of a frame-trotting jog dial) and control pitch. In other words, the basics of the CDJ were there from the start.

The CDJ-500 also added a handful of features that couldn't exist outside the digital realm: it could loop on the fly, and its "master tempo" function let you change speed without changing key. With the CDJ-500, Pioneer was pitching a CD player to clubs, but they didn't have their sights set on replacing the 1200s. As Hart notes, brochures for the CDJ showed the decks installed in the booth above the usual fleet of 1200s.

The line would continue evolving through the '90s. The CDJ-500II, arriving in '96, provided longer loop times and improvements to the master tempo. Then in '97, the CDJ-500s (or CDJ-700, as the American model was dubbed), became the first deck to really take off in nightclub installations, shrunk its height considerably and added "oil-damped shock absorption" for improved stability. By the time the entry-level CDJ-100s hit stores in 1998, the line had begun to resemble its current form factor—albeit with a trio of now-quaint onboard sound effects.

The 2001 arrival of the CDJ-1000, though, was when CDJs truly started to emerge from the Technics 1200's long shadow. Interestingly, this was the result of acting more like the turntables that inspired them. (The rapidly dropping price of CD recorders and the emergence of download culture didn't hurt, either.) CDJ-1000s featured Vinyl Mode, which allowed you to scratch with CDs, and a touch-sensitive jog wheel with its own animated display. Even if CDJs were now about as interactive as 1200s, they had a different feel, and the presence of super-quick cue and play buttons (and the ability to save cue points onto an memory card) gave them functionality 1200s just couldn't match.

In a set like DJ EZ's at Boiler Room from 2012, you can see the sort of wild performance this more mature CDJ engendered. The cue button becomes a sample trigger. Loops double as stuttering sound effects and transitions (unhindered by tempo drifts or dusty skips) can be as massive as your imagination (or good taste) allows. You can still use them creatively, even if you're not putting on an EZ-style show. Gerd Janson, a resident at Robert Johnson and a Panorama Bar staple, likes expanding tracks with the loop function—"loops in, loops out and loops in the middle"—and by playing instrumentals and "doubles" across linked decks. And even if you're just blending records, there's also the undeniable fact that you can achieve more effortlessly smooth mixes with them.

"To play vinyl, you need more flair," says Mannheim's Nick Curly, who's been using CDJs as his primary deck for the last few years. With the Pioneers, "I can focus more on the mix and communicate with the crowd."

Much to the chagrin of purists, some of the features that have come since—tempo syncing, quantized loops, a Slip Mode that lets you scratch while the current track keeps rolling in the background, even software that suggests your next track based on key—have sought to make mixing with CDJs even more seamless.

It's difficult to argue, though, with the most full-scale change Pioneer has introduced to the line: eliminating the need for CDs altogether. Though first floated in the ephemeral CDJ DMP 555 in 2002, play from rewriteable data storage devices didn't arrive in earnest until the more consumer-oriented CDJ-400 in 2007. And it wouldn't reach its apex until the CDJ-2000 in 2009, when you could link multiple decks via an Ethernet cable. DJing without physical media has been around since laptops popped up in the booth in the early 2000s, and there are plenty of cheaper controllers that can do more or less what CDJs do. Not having to reconfigure the booth between every performance, though, is priceless—as is slimming your "crate" down to a USB stick. With the Nexus version of their flagship deck, you can avoid sticking something in them altogether and simply beam music from your iPhone.

But doing away with physical media isn't just a space-saver. Audio CDs are limited not just by space—a measly 80 minutes at most—but by audio quality (16-bit samples, as opposed to meatier 24-bit ones), burn time and physical damage. They're also almost certainly less relevant to most DJs than vinyl records at this point. With the current system, you can crouch under the booth, bounce down your latest track at the same high fidelity as your DAW session and start mixing it in about a minute. CDJs have now brought turntable-style control to music as it all too often exists now: shapeless, unsigned, fast-moving and ever-multiplying. You have to wonder if the fast-evolving CDJ, once seen as a supporting actor to the almighty Technics 1200, has finally usurped it. Gerd Janson, though, points out one place where CDJs will always fall short for a certain type of DJ: "You cannot insert records."