Feature

In Conversation: Mark Ernestus and Arthur (Hard Wax, Open Ground)

Written By:

Phil Cho

June 3, 2025

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Mark Ernestus and Arthur speak on Open Ground, Hard Wax, and Ndagga Rhythm Force ahead of their upcoming sets in Los Angeles on June 8th.

Wuppertal is a city you’ve likely never heard of. Located four hours from Berlin by train, the city is mostly known globally for its unique suspended monorail and the Wuppertal Dance Theatre, which was founded by neo-expressionist choreographer Pina Bausch. However, since December 2023, word has steadily been spreading that Wuppertal is now also home to one of the best clubs in the world.

Founded by Markus Riedel and Mark Ernestus (Basic Channel, Rhythm & Sound, Ndagga), Open Ground “strives for a great sound-system music experience – in an inclusive, respectful environment. Committed to originality, independence and expanding horizons.” Located inside an underground bunker, the club has close ties with legendary Berlin-based record shop Hard Wax, and is seeming to be on a similar path of global influence and notoriety. Just this year, Berlin-based culture magazine 032c wrote “The Best Club in Europe Is in Wuppertal,” and dance music hub Resident Advisor reports “Is Open Ground the Best-Sounding New Club in the World?”

I spoke with Mark Ernestus alongside Open Ground music director / Hard Wax shop manager Arthur Rieger ahead of their upcoming sets for In Sheep’s Clothing, In Between, and Interval Agency’s open air event on Sunday, June 8th. Tickets are available now on Resident Advisor. Don’t miss it…

Hey Mark and Arthur! There’s a lot to cover, but I wanted to focus on Open Ground, the project that you’ve both been working on over the past few years. There was a quote I saw where someone said it was "The most pure vision for a club I've ever experienced." I’m wondering - for each of you, what was your vision for what Open Ground could be and how is that playing out?

Arthur: It’s funny talking to you about this now because last time I was in LA, it was shortly before the opening, so I had no idea what would happen with the club. I had just gone to one test event in November with Fadi Mohem, Elke, and Lil Mofo. This was the only visual & hearable thing to feel after all those years of talking about it and being on the construction site. Now it’s been one and a half years since opening…

To do this project in Wuppertal is pretty ambitious on all different levels because there’s not really a scene for what we do with the curation. Especially because for a lot of the people that we book, it’s their first time coming to Wuppertal. The city is also really specific in terms of the community coming here. There are different layers of what audiences you can attract. There are around 15 million people in the North-Rhine Westphalia area, and each close city has a really different character.

Then, you have the national and international aspect. Wuppertal is quite central in Europe. Brussels, for example, is around two and a half hours by train. Berlin is four hours. Paris is five hours away. Amsterdam is around three hours. You can also go by train from London. So you have these different layers of heritage with the audience. Before opening up, this was the most interesting aspect to see what people are coming, how the people from the area are reacting to it, how is the mixture of people, and how is this all working out on the dance floor?

“We’re coming from a record shop environment. So I see music genres as something quite universal. Giving people the chance to expand their mind to explore new music, that’s what is really interesting.”
Arthur Rieger

Mark: When Markus Riedel–who runs Open Ground–first called to tell me about the possibility to turn this bunker into a club, we both had the same thought: if you want to do something that’s worth anyone’s while, it needs to speak to people way beyond Wuppertal, which is a city of 350,000, but located in the middle of Germany’s biggest urban area.

Most of the initial core team have a music and record shop background, some working at Hard Wax for many years, so the careful curation and good sound are top priorities, but of course it’s worth nothing if everything else isn’t right, either. Markus and Christine were living in Berlin from the mid-eighties to 2008, so they have many points of reference back from the very early 90’s club scene. And myself, occasionally DJing in many different places over the years, I have experienced a lot of situations that made me think this could and should be done better, especially the lack of acoustic treatment.

From what I’ve read, it seems like the acoustic treatment of the room was equal, if not more important to this project than the sound system?

M: They are not separate things, the sound experience is a result of both, for better or worse. The best sound system is wasted if put into an untreated room.

The main room of Open Ground is called Freifeld, named after “freefield acoustic simulation,” a setting where no sound reflections occur. Can you talk about that and how people have responded to the room?

A: We actually recently had a lecture last week at the University of Düsseldorf on the story of Open Ground with Markus, Mark, me, and Willsingh Wilson (wax-acoustics), who did a whole acoustics presentation about why the room sounds the way it does. There was one person in the audience who said they had a really great experience at Open Ground and had the feeling that this is different from other clubs. Something is different here. It was interesting to hear the direct feedback not just about the sound experience, but also how you get treated to get in, and all those details in between.

The priority is to be in a room, where you have a chance to fully get into the sound, and also to share an experience together. The experience is not only about the music. It’s really important how the room sounds and the physical reaction to it, but it’s also about how you feel, and the state in which you are able to receive certain music. We have two rooms at Open Ground, which is nice to have this dynamic of different room situations. In a lot of clubs, when you’re in one room, you can hear what’s happening in the other room, and it’s this clash of sound that makes absolutely no sense. Here you have two rooms where you don’t even realize there’s another room because you can’t hear it.

I think the sound system works in a way where another dimension opens up in each room. You might have a Techno lineup in the main room, and then you go into the small room where there’s Drum & Bass, Grime, or something else. You might not usually be into that, but because of the sound system and the room, you can really understand the full spectrum of sound being played. Like Mark was saying, we’re coming from a record shop environment. So I see music genres as something quite universal. Giving people the chance to expand their mind to explore new music, that’s what is really interesting.

Speaking on that record shop point, Hard Wax has exposed so many people around the world to new music. Do you see Open Ground as an extension of the store and what you're trying to achieve there musically?

A: You can’t deny where we’re coming from and where we spend a lot of time, but I don’t see it as an extension or an outlet of Hard Wax. I’m sure there’s a closeness. It’s absolutely in the DNA, but there’s something different because the environment here is different. It’s not Berlin or another big city. A record shop is also a community-based place where people come to hang out together, but I think clubs in general have a different dynamic. What we’re doing here is to show each genre and try to present it equally. For example, a niche that’s not so popular in mainstream music, like Dub or Reggae, I don’t necessarily see that as something on a small floor and Techno on a big floor. We’ve had evenings with Dub, Reggae, or other specialist music on the bigger floor and more “categorized” music in the smaller room. For some people, they couldn’t understand it, but I think this is important to show that it’s possible.

M: The way I would put it, as Arthur said, is there’s a lot of the DNA from the Hard Wax bubble in the club, but Open Ground is a different operation in a different environment. I’d say we have common core values. Sometimes people tell us they thought they weren’t into this or that genre, like Dubstep, Drum & Bass, House, Amapiano or they didn’t even like going to clubs, but when they had the full experience in the room, it felt great and they loved it. And that’s the most rewarding thing, to see people discover new things rather than just having their expectations met.

A: Another example, we had Chez Damier play at Open Ground last December. That was really special in terms of the community here that maybe hadn’t experienced house music in that way before. For me, it was really fundamental, like a new chapter in the community. I heard there was a young guy there who was into super fast-paced techno, and never really experienced house music. He was converted after that, and now he’s like a proper house head. This one night changed his life. That’s amazing to hear.

“With clean sound, it’s easy to find the volume that is loud enough, but not too loud. It sounds so trivial, but in reality, it’s a rare situation.”
Mark Ernestus

Speaking of the sound system itself, Funktion-One built the system at Open Ground. Can you talk about working with the team? I heard the system utilizes a subwoofer that was developed somewhat recently?

M: In Freifeld, we have two 32-inch horn-loaded bass speakers for massive, effortless sub-bass. In the small room, Annex, there’s one of them. That’s very powerful, of course, so again they only make sense indoors if you have very effective absorption down to the lowest frequencies so that you ideally hear only the direct sound from the speakers, and not a random mess of room reflections. And then you don’t need more than 100 db to feel fully immersed in sound. I’d say it actually feels more intense than ear-damaging levels above that. Every DJ knows this vicious circle where you want to hear more, but when you turn it up you hear an even bigger mess. It’s too loud already but still doesn’t feel loud enough. With clean sound, it’s easy to find the volume that is loud enough, but not too loud. It sounds so trivial, but in reality, it’s a rare situation.

(Read more about the Funktion-One soundsystem at Open Ground: https://funktion-one.com/news/open-ground-puts-wuppertal-on-the-map-with-incredible-club-experience/)

Arthur - you handle the music programming at Open Ground. What is your approach to the lineups at Open Ground? It seems like it leans into bass music and techno, but also extends into house, disco, reggae, and other genres?

A: We do it as a team with Chris Parkinson and I together. The situation is quite complex in terms of the area, the community, and what people are into, especially if you’re not only limited to one or two genres. Some people in the local newspapers described us as a techno club, but it’s completely not true, and created a lot of misunderstanding that luckily does not exist anymore. The longer the club is open, the more people are getting the bigger picture. Some people come in and think, “I don’t know what kind of music this is, but it sounds amazing.” With the room and the sound system, it opens the door to that. This is a big part of the idea behind the lineups.

Also, I think it’s a big responsibility these days with booking and curation to not just look at social media likes, or stuff like that. I understand that these days a lot of clubs suffer and need to make money, but I also think it’s quite a factor to see potential that is not there yet. For a young artist, playing on a proper sound system is really powerful. It shifts your mindset completely. You’re hearing stuff that you didn’t hear before, and you grow with that experience.

It’s interesting, it feels now after the first year, there is a new chapter in the demographic of the community and the curation that is happening. We’re trying new formats. For example, we have a format called “Extended Club Nights,” and they go to 12pm in the mid-day. Then we’re also trying a different format where we’re starting earlier in the day, just to be able to listen to music together. Some DJ’s might even play two sets in one night, which gives them the freedom to play something out of the box, and maybe play some things they don’t have the chance to show usually when they play out.

“There’s a lot of the DNA from the Hard Wax bubble in the club, but Open Ground is a different operation in a different environment. I’d say we have common core values.”
Mark Ernestus

I saw there’s a Barulho World takeover next month. Is it also a mission of Open Ground to introduce people to contemporary club sounds from around the world?

A: I mean, it’s not like we opened up and had a planned program done months in advance. It has to grow with its surrounding. It was always first seeing the reaction after the action, and having a dialogue with the surroundings. But you can’t deny that a lot of contemporary global bass music, especially Amapiano, Gqom, and stuff from South Africa that is coming out right now, is absolutely amazingly produced. If you play that stuff here, it feels like it was made for the sound system. It’s for sure worth developing a certain awareness for new music, especially that music. We are starting to include this into the lineups more and more, and the reaction so far has been really good.

Open Ground has also presented a concert series (previously Tikiman, Holy Tongue, MOIN, Rashad Becker, and others). Ndagga Rhythm Force will be performing live for the second time at Open Ground at the end of June. How was that first show last year?

M: Really good. It was also the opening concert for the tour, as it will be this year. That’s ideal for us because we can do rehearsals and the band are comfortable there with Café 23 upstairs, the rooftop terrace, and the whole environment in general. But more importantly, it is crucial for the musicians to hear each other really well because the percussion patterns are very dense. The monitoring is always challenging because sabar drums are super loud so the monitoring on stage is super loud as well, but Open Ground’s “free-field simulation” works great in that regard, too. And of course, good working conditions for the musicians translate to a good performance.

The group has released its first new record in nearly a decade. Was there a moment that sparked the new release?

M: No, it has been a slow process. After the last album, I didn’t want to just continue with the same approach. When we play live, one track can be 25 or even 30 minutes long, without losing attention. Recorded music and live music are different art forms, but after playing live so many times, I was intrigued to have more of this extended, free flow in the new tracks. They are, of course, amazing live musicians in many ways. Not just the playing itself, but also for that awareness of the right moment. When is it time for you to take the lead? When is the moment for you to step back and give room to the others? And with that, there’s always the right amount of improvisation and a great balance between repetition and variation.

You've been performing together now for a long time. Do you feel like the sound has evolved over all these years of working together?

M: Yes, for sure. It’s always a bit different because they are always in the moment. We had a very stable group for some years and recently we had a few changes. You learn a little from each night. We’re always tweaking stuff. We use different technology, different synths over the years, and we try out different things. I think we’ve played roughly 150 times now, but it doesn’t get boring for me still. Every night you have another different little influence. Every night someone else is in his or her best shape and takes a bigger role.

You’ve worked extensively with reggae over the years. For you, what is the link between reggae rhythms and the Senegalese mbalax you’re exploring with Ndagga Rhythm Force?

M: It’s not a conscious decision for me, but the musicians sometimes tell me they feel reggae in the tracks, or sometimes techno. Last year when we started to rehearse the tracks from the new album, some of the musicians were struggling, especially the drummer, to find the right place in the groove. The kick or the keyboard were not where they would expect it to be in a Senegalese mbalax context, but that’s what makes the groove.

Mark, you are touring once again after taking a bit of a step back in the last few years. I believe the last time you were in Los Angeles was in 2019 for Dub Club. What are your thoughts coming into this tour after so many years?

M: I really enjoy getting around, playing, and meeting people across the world, but with all my other work responsibilities, it’s difficult to be away from that too often. I try to keep it essential.

What about you Arthur? This will be your second time touring the United States. What are you excited for?

A: I’m really happy to join Mark on this tour. For me, it’s interesting with the timing because I’ve been listening and digging contemporary African music for a few years now, but I’ve never really played it out in clubs. In Berlin, there’s not really a scene for that type of music. I never hear anybody playing it out. I’m really curious to play that stuff on this tour because after playing it at Open Ground, it was a really shifting moment for me when I realized the power of that music in a context where people are dancing to it. It’s so much fun. I’m mainly looking forward to that, but I will also play reggae, if possible. Let’s see…

Lastly… We always try to include music within our features, so I’d love for you to share some records that you enjoy playing at Open Ground or some tracks that you might play during the tour.

Teno Afrika & Diego Don – Storytellers

A: This came out in 2021 and immediately caught my attention when it was released on Awesome Tapes from Africa, which is run by Brian Shimkovitz. He is constantly releasing so much amazing music for so many years. It’s pure joy to go through his catalog. All the Amapiano-related records on his label, I can highly recommend to anybody who wants to get into it. It’s always fascinating with tunes that have unexpected turns or bridges, but somehow come back to the original idea. That’s totally the case here with “Storytellers.“

Shaunmusiq & Ftears x Xduppy feat. Myztro, Mellow & Sleazy, QuayR Musiq & Matuteboy – Bhebha

A: Not sure if this is to file under Amapiano, feels more like a proper Bass cut. If I understood it right Bhebha is a dance but can also mean something related like to swagger. Heavy.

Jay Music – Isgubhu

A: Ama style is mostly around 112 +/- a few bpm, so the groove is quite steady. I can’t agree at all with people saying Ama stuff sounds all the same. Sure, there are often the same shakers or other sounds used, but there are so many elements or arrangements where I’m thinking, “How did you come up with that?”, and they have somehow interesting tempo changes like here.

Mr JazziQ – Crows

A: Being a music junkie and working at Hard Wax for over 10 years now, I’ve spent a lot of time listening to all kinds of music. With Amapiano, I love the use of seemingly unusual sounds and also the use of voices in a production more as an instrument rather than mainly as a hook or singing phrases. For example, like Gussie Clarke did in the late 80s/early 90s raggamuffin era in reggae. That’s pretty Techno to me, and I wish a lot of Techno these days would not be so conservative in their productions.

“Crows” feels also a little bit like a twisted Deep House thing to me. In general, some Ama stuff feels to me like an extension of certain ’90s NYC / New Jersey house cuts, but just amazingly sharp and well produced, but in the same way very playful.