The changing digital music market has not been kind to the mix CD. Many people download their music or listen via streaming services, and even those who still prefer the physical product are more likely to collect vinyl than buy a CD. More troubling still was the advent of the podcast, which has put mix CDs between a rock and a hard place. With so many DJ mixes available for free online, why would anyone pay for one?

These tough conditions have had a real effect on some of dance music's biggest players. Global Underground have all but stopped production of their blockbuster series, which in its heyday featured the likes of Sasha, Steve Lawler and Paul Oakenfold. UK juggernaut Ministry Of Sound has diverted energy away from the format and towards compilations of unmixed tracks. And once venerated series like Balance or Body Language don't command the same attention they used to.

Live At Robert Johnson is a more recent story of the format's demise. Renowned for its careful execution and curation, the CDs paired beautiful packaging with eclectic selections and became one of the best-loved mix series of recent times. But after three years and eight volumes, Robert Johnson pulled the plug after Dixon's masterful instalment, citing the pointlessness (in their opinion) of a product that limited the DJ to 80 minutes. Dixon himself claimed it would be his last mix CD.

It wasn't always this way. In the mid '90s, a mix CD was how your average punter heard dance music outside the club. Not everyone collected 12-inches after all, and the early internet didn't provide a niche perspective the way it does today. The most popular mix CDs created trends and supported new genres, steering the evolution of dance music and shaping what people would expect to hear in clubs.

It's difficult to talk about mix CDs without mentioning Sasha & Digweed, whose 1994 Renaissance: The Mix Collection helped popularize the format. Its three discs gave listeners around the world a concrete idea of what Sasha and Digweed's music was all about, turning the sound of UK superclubs into a global phenomenon. The Mix Collection propelled the duo further into worldwide fame. It was followed by the equally legendary Northern Exposure, a high-water mark for progressive house.

Mix CDs were a way for DJs to make a living purely as DJs—something that's become increasingly rare in an age when DJs get booked for their records rather than their mixing. And beyond the novelty of listening to a club set at home, mix CDs offered a unique opportunity for DJs to cater to a home listening audience, showcasing their taste and curatorial skills. !K7's DJ-Kicks series, Michael Mayer's Immer, Sasha's Involver, Richie Hawtin's many mixes and the conceptual Grandfather Paradox by Henrik Schwarz, Âme & Dixon have all made the same kind of impact that any artist album could have.

New entrants have come and gone, venerable series have fallen to the wayside, but a few labels continue to battle with the market even as they face increasingly harsh conditions. A mix CD has more than just physical capacity limits working against it. It's a format that takes a significant commitment to prepare—up to a year in some cases. Compare that to a podcast, which could theoretically be finished the same day it was commissioned.

Then there's licensing. Easily the biggest hurdle when it comes to putting together a mix CD, licensing can be a major obstacle to artistic intent. Since a CD will be sold and profited from, the label releasing the mix needs to reach licensing agreements with every artist or label included, which costs time and money. This puts the kibosh on almost anything from a major label, whose licensing fees are beyond the budget of most dance music labels. Tunes that have uncleared samples and unofficial edits are out, too, as are records that are simply lost to time with no clear rightsholder. None of this is an issue in the comparatively lawless internet realm.

To make things worse, releasing a mix CD into the online realm only presents new challenges. Some digital retailers, notably iTunes, require labels to include unmixed versions of every track—an unappetizing prospect for artists, especially when it comes to unreleased tracks. "There's an agreement where a certain percentage of tracks can be bundle-only," says Ministry Of Sound's head of compilations, Alice Schofield, "and they're being more flexible on that, but that's the biggest licensing restriction."

The internet also blurs the legal boundaries between territories, making it more expensive to license certain music. "Back in the old days, !K7 would license the tracks for Germany," says !K7 A&R man Phil Howels, "and then would basically use the fact that they're exporting records around the world to get around the international licensing requirements—like the 2ManyDJs As Heard On Radio Soulwax disc."

"The Kruder & Dorfmeister DJ-Kicks is a compilation which includes 90% music controlled by the major record companies," !K7 founder Horst Weidenmüller says. "The record has never been released online. The record was only created for Germany, because we couldn't get the rights for international. We sold one million records in the meantime on export, and you can't repeat that on digital." If you're wondering how a mix could possibly sell over a million copies, well, Kruder & Dorfmeister's was released in 1996. Nowadays the story is different.

The fabric and Fabriclive series, which have been running since 2001, might be the best-known standard-bearer for the format. These mixes aim to replicate the sounds and sensations of clubbing at one of the world's best venues. It wouldn't be a stretch to call them an ongoing success story—today they're about to hit their 150th release.

"The mixes offer people something of the fabric experience at their own convenience if they are unable to come to the club—prohibited by distance or age—or if it's just a Wednesday morning commute to work," explains fabric label manager Leo Belchetz. "It also allows us to show our support for artists, either by highlighting our long-standing relationships with established acts or by providing up-and-coming artists with a platform. I think the mixes are an embodiment of fabric's commitment to music."

A fabric mix carries enough gravitas to be desirable in and of itself. "The very act of being included in our series gives a mix a permanence and longevity that most free online mixes don't have," Belchetz says. "The fact that our mixes are for sale puts an increased impetus on our contributing artists to go the extra mile beyond what they'd go when compiling a free mix. Then, of course, there are things like the professional mastering to ensure the music sounds at its best, the visual artwork, and the packaging on the CD version, which we went out of our way to make special from our very first release."

Berlin's Watergate, another club with a major mix series, got in the game relatively late, in 2008. Their mixes place equal emphasis on club residents and prominent guests, mixing local staples like Marco Resmann and La Fleur in with Kerri Chandler and Solomun. "We started our label and the CD series in 2008 to showcase what was happening inside the club," says Watergate's Alex Knoblauch. "The artists taking care of our compilations are aware of the high level we're keeping with the series, so they put in the maximum effort, which you can hear in the final mix. We're getting great feedback about the artwork as well, so people seem to be OK spending a bit of cash for these mixes and we're very happy about that."

They see the CDs as a pragmatic promotional tool more than anything else. "It's not only about the compilations," says Knoblauch. "We're putting together a full campaign around the respective artist—the CD is backed by EPs for the exclusive tracks, we're launching extensive release tours booked by our agency, having release parties at the club. The CD is just one aspect of a whole."

It's important to remember that fabric, Watergate and like-minded series such as Rinse are projects by outfits that make money in other ways—the first two, after all, are successful venues in major cities renowned for their nightlife. The stakes for other series, like !K7's DJ-Kicks, are higher.

###

A freeform series that lets DJs do pretty much whatever they want, the idea behind DJ-Kicks has informed the pioneering German label's relationship with the mix CD all the way back to the early '90s. Weidenmüller describes their earliest attempts (with the X-Mix series) as "a fairly weird home listening experience which kind of coincided with that period in the middle of the '90s where music was pretty eclectic," a concept that carried over to DJ-Kicks. Launched in 1995 with a mix by CJ Bolland, with landmark entries from Scuba, John Talabot and Maya Jane Coles in recent years, it's another brand that has managed to weather the storm of the changing market.

"These are about telling stories," Howels explains. "Wolf + Lamb vs. Soul Clap['s CD] is a really good example. It was one of the first ones with very heavy exclusive material; it had about ten exclusives on it, which brought a lot of character. The parties had the same spirit as the record, and that's a good example of how we would ideally approach and promote a DJ-Kicks now, to make it more special in the environment that we now live in."

Even though they've generally pulled back from the format, Ministry Of Sound have also launched one of the most lauded new mix CD series in recent years with Masterpiece. The three-CD set, which has featured Carl Craig and Andrew Weatherall, focuses on veteran artists and gives them an extended platform. "It's their masterpiece, all the stuff that's influenced them," explains the label's head of compilations, Alice Schofield. "Which means the tracks can be more eclectic, a brilliant collection of tunes."

Masterpiece is an example of how labels can adapt to a new market and its new set of expectations. Beyond the lofty heights of the title, it's a deluxe package that takes considerably more effort to compile than your average club set—and it shows, offering fans a deeper look into their favourite artist than you could get from most podcasts.

Though nearly everyone admits that their sales are down, troopers like fabric and Ministry Of Sound insist that CDs are still viable, even profitable. !K7 say they make money from them, and Ministry Of Sound concurs. "Young clubbers who are really into their DJs and heroes [buy them]," Schofield says. "There's an older audience, too, for the DJs they grew up with—like the Masterpiece series. Andrew Weatherall's did really well. I wouldn't say there's a shift towards podcasts, because I think the people that bought them buy physically still."

"We still sell more copies on CD than digitally," says Belchetz. "We do keep an eye on the cost of licensing each release to ensure it's commercially viable. Though I'm not suggesting sales of the format aren't declining, I feel the death of the CD is wildly over-exaggerated in the press if you actually look at the volume of CD sales."

Not everyone is as fortunate. Ostgut Ton, the label behind the Berghain and Panorama Bar series, last week announced it would stop manufacturing them altogether. Starting with the sixth installment of Panorama Bar, Ostgut will offer a few online mixes a year, heavy on exclusives and released infrequently enough to keep them special. They'll be offered as free downloads, with a licensing policy that requests the rights to a song at no cost for a period of three years. It's a clever solution that also takes the money out of the equation entirely, making the product a labour of love (and a handy promotional item) rather than something to make a buck from.

In an interesting twist, and perhaps as a reaction to the market saturation of free podcasts, a number of new labels have entered the fray—Bass Culture, FXHE and Token have used the format to advertise their wares in the way your average punter consumes a 12-inch in the first place: woven into a DJ set. Token's mix, Introspective, was easily one of the best mixes of 2013.

"You wouldn't have asked me this question [about mix CDs] if I'd just released a podcast," says Token founder Kr!z. "Anyone can do a podcast. I guess doing a physical release just makes you stand out in some way. There's also the artifact—the packaging—which gives it a more personal feel than an mp3 file. I like to put out tangible pieces of art. You could call me old school."

For Kr!z, the ends justify the means. "Sure they're profitable. There's a different production cost, different margins. It's hard to compare—a compilation or full-length usually gets more press attention than a single, which makes it available to a wider audience. And that is the best profit you can have with this, and also the main purpose of the label: to put out great and timeless music I really believe in, and to reach the largest possible audience."

His idea seems to define the format's modern role in a larger sense: at this point the mix CD is more of a symbolic gesture than the massive industry concern it once was. People will pay attention to a mix CD because of the effort and care it represents, even if they might not buy it—a fabric instalment, for example, carries more weight than almost any podcast series you could name. This puts mix CDs in a tricky grey area: their success is arguably measured by the buzz they create rather than sales figures, but they still need to sell to survive.

Some, like Belchetz, have hope and insist that people will continue to buy mix CDs to support the artists and music they love. "The notion 'why would anyone buy mixes when you can get them so readily for free?' can be applied across the whole recorded music market," he says. "In my opinion, if you ask that of mixes, you have to ask it of any format."

His point that all physical media faces a similar challenge is true, but there's no denying that mix CDs in particular are an endangered species in the wilderness of the music industry in 2014. You can press a 12-inch in a limited run of a few hundred copies and break even, but a mix CD's financial overhead is much higher (and its profit margins lower), primarily due to the licensing costs involved.

Watergate's Knoblauch admits mix CDs have evolved into more of a "collector's item," a niche format that a dedicated bunch will continue to buy even as the rest of the world moves on.

Mix CDs are still relevant to dance music. We listen to them, we talk about them, and we use them to gauge the rise and development of DJs. True, a lot of us don't buy them anymore. But as long as there are people scooping up DJ-Kicks and fabric, they'll be around for a while, and creative labels will find new ways to adapt. It's a harsh environment, but it's not inhospitable just yet.