How do DJs approach harmonic mixing?

Erol Alkan, David Guetta, Flava D, DJ Puffy and others explain how they use and think about an arguably overlooked area of DJing.

Like many topics in dance music, harmonic mixing, or mixing in key, as it’s also called, can spark passionate debate. People enjoy discussing its value, its necessity, and even its definition. All of the DJs we spoke to are, naturally, advocates for harmonic mixing, but they also appear to hold it lightly, knowing that ultimately the technique is a question of personal choice. Let’s pull back for a second, though, and clarify what we actually mean by harmonic mixing, while exploring some of the key questions it tends to throw up.  

In Western music, most songs or tracks have a key, a set of notes that relates to a scale. There’s a single tonic or keynote, which can be thought of as a song’s home—we say, “This track is in C minor.” Even if we don’t know why, we get a sense of resolution when a song returns to its “home” note or chord. It somehow feels right. 

It therefore follows that when a DJ mixes two tracks in the same key, or in musically related keys, it will sound… not better, necessarily, but more stable or smooth or yes, harmonic. On the other hand, even if the tempos of two tracks are perfectly matched, there can be something about a mix that feels off. A likely explanation is incompatible keys, or a “key clash,” as DJs often call it. (We won’t get into the weeds of the music theory behind compatible keys here; it’s enough to know that the popular understanding has been that there are four possible keys you can mix into, although there are in fact six.)   

Here are two quick examples I mixed in rekordbox. I chose amapiano tracks as the style’s melodic richness makes easier to hear what’s going on. Both track A (JazziDisciples’ “Weyo”) and track B (Kabza De Small’s “Sponono”) in this DJ mix are in the same key. See what you think. 

Now listen to this mix between track A and track C (Ntokzin’s “References”), which is in a musically unrelated key. 

Could you tell the difference? Did you prefer the first mix? Does this interest you? 

This is harmonic mixing in essence. It’s a method of selecting tracks based on compatible keys because at root you, the DJ, like how it sounds.

There are other approaches. Some DJs might use keys to intentionally create dissonance, or play with the energy of a room by, for example, ascending a musical scale. And many DJs will say that harmonic mixing is something they do intuitively, building a sense of what works through experience. But fundamentally, harmonic mixing is pretty straightforward. 

The debate, however, tends to stem from related questions. Do DJs limit themselves by choosing only harmonically compatible tracks? Can an audience tell if a DJ is mixing harmonically? And following from that question, is the value actually that people sense harmonic mixes rather than knowing them? Is harmonic mixing relevant for someone playing, say, minimal techno? Questions like these were clearly on the DJs’ minds as they gave their responses below. 

Whatever your view, there’s no doubt that these days harmonic mixing is far more accessible than it used to be. I personally became interested in the early 2000s, after reading a relevant chapter in Bill Brewster and Frank Broughton’s influential 2002 book How To DJ (Properly). At that point, the Camelot Wheel, which gave keys a more easily understood alphanumeric code and displayed these codes on a wheel, had become an essential tool. As Brewster and Broughton outlined in the book, though, finding a track’s key meant manually playing notes on a keyboard until you found its keynote, which you checked by playing a chord or a scale over the track. Needless to say, this was a faff. 

Even so, “It wasn’t that niche,” Brewster told me. “Obviously it wasn’t something that the majority of DJs were doing or even necessarily had an interest in, and it did depend on the style of music they played, but it had certainly been discussed and there was an awareness of it existing. Sasha, for example, was notable for using it quite a lot and many of the prog house DJs would use it for those long overlays that they would do.”

These days we have it comparatively easy. Mixed In Key, the key detection software that stemmed from the Camelot Wheel, provided DJs with an early technological solution when it was first released in 2006. Over the years, key information has become available in download stores like Beatport and Traxsource, while popular DJ software like rekordbox, Serato and Traktor all have key detection systems. The recent CDJ-3000 has gone a step further with the introduction of the Key Sync button, which adjusts the key of the next track to match the track on the master deck, and Key Shift, which lets you manually shift a track’s key. Even if the technique isn’t necessarily in widespread use, the options for exploring harmonic mixing have never been greater. 

Indeed, it took some time to find relevant DJs for the piece, and those we spoke to all seemed to approach harmonic mixing from a slightly different angle. We asked them to outline their personal philosophies and techniques, and to offer advice for anyone considering getting started. The ideas behind it have been around for decades, but we might still say that harmonic mixing is a curiously under-explored area of DJing. 

Erol Alkan

“It’s an incredible tool, I couldn’t imagine not being able to use it”

I’ve been aware of harmonic mixing going back to the ’90s. I always made notes as to which records worked well together, so when it was possible to carry all of this inside the rekordbox system, I knew it would open up a whole world of possibility to me. 

The ability to have key information at your fingertips is a great progression for how I approach putting records together. I do feel that it can hinder your track selection if you only look for records which will fit, as part of the excitement of DJing comes from unexpected happy accidents which nobody may have logically thought of. I tend to use it in several ways to help lead me to what I feel is right—and I truly love it—but I never let it dictate my decision. I’ve been using it since 2010, ever since I started using rekordbox. 

I’m never concerned about my mixing being too slick, but there is a certain point when key clashes can be as horrid as clashing rhythms, which I regard as big a problem. I suppose how big that problem can be is in the eye of the beholder? There is also the added factor of using the Master Tempo control, and how that can adjust the pitch of each track if you don’t have it selected. This can render the key information useless but it can also help knit together some records where you heavily switch up/down the tempo. I’ve accidentally come across some interesting moments that way.

My first judgement is always to read the room and connect with the feeling inside of it.

Nearly every DJ I know pays attention to the harmonic keys of their music, but they all have varying degrees of how it limits their choices, and that is the overall result I take from this technology. It has really helped at times, and led to some inspired choices I may not have thought of. But at other times, I have been 20 minutes into a set and realised I didn’t need it that night. It’s an incredible tool, I couldn’t imagine not being able to use it. 

Flava D

“It can really make or break a transition” 

For me harmonic mixing only became important about a year ago, when I had the chance to watch back a mix I did for an online stream. I’ve always proudly freestyled my sets, but as I was sitting on my sofa I was able to pick apart any habits that I may miss whilst playing in a live, loud, energetic environment, where it’s easier to cover up a key clash. 

It can really make or break a transition. Mixing two tunes with the same key can really enhance the moment, as it just flows a lot better. There’s nothing more fun for me than mixing a big vocal into another drop with a slammin’ bass that fits perfectly in key. Those moments can create the biggest reactions in a rave when done well.

So for me key clashes are undesirable, although I feel that with some styles of mixing it isn’t as important. If you’re a DJ that specialises in big drops rather than the more melodic side, then being perfectly in key doesn’t matter as much. Not mixing perfectly in key during every transition doesn’t make anyone a bad DJ.

I am pretty basic when it comes to the tools I mix with. As long as I’ve got three decks I’m good to go whatever the situation. But I do have a lot of fun when there is a RMX-1000. With this I can freehand drums or effects during a breakdown of a track that’s playing and make it my own.

Key mixing isn’t something I’ve ever asked anyone around me about, to be honest. It’s something I’ve only paid attention to more recently, but I’d definitely be curious now as to how people feel about it. I personally never focused on keys during my early days because I am not trained in music theory, so the idea of having to know what key this tune or that tune is intimidated me. But since I’ve discovered the Camelot Wheel setting, it’s literally changed my whole mixing game! With just a click in the rekordbox settings I was able to see what tunes would be compatible with each other in a really simplistic way. 

David Guetta

“Harmonic mixing is absolutely essential in my opinion”

In the same way there is a difference between a normal transition and beat matching, there is a difference between beat matching and beat matching with harmonic mixing. It’s just level two. This is, in my opinion, what separates good from great. It kills me when I hear a DJ mixing two records in clashing keys for a full minute. Harmonic mixing is absolutely essential in my opinion. I’m so happy about this new function [on the CDJ-3000]. I used to prepare my sets and change the key of some of my records to be able to put them in the order I wanted, so this is gonna save me so much time.

Sef Kombo

“I feel like mixes tend to sound a lot smoother on the ear”

Mixing in key matters to me a lot, as I feel like mixes tend to sound a lot smoother on the ear as you take the listener on a journey. As I’ve gained more knowledge and experience about the tracks I like to play, I developed an understanding about what fits and what didn’t.

My philosophy is quite simply to always get from start to finish in my mix seamlessly.

The tool I’ve used for many years now is Mixed In Key. Upon using it, I confirmed that I was already on the right track with the key thoughts I was having in the first place without using any tool. 

I think in the club setting, key clashing is not a terrible thing when you are just hyping the vibe up. Sometimes the use of the EQ and the filter can help along the way—it’s good to keep a clash to the bare minimum within a set.

I haven’t had conversations with other DJs about mixing in key, although when listening to those around me, I figure that they maybe subconsciously are already doing it to ensure the mix sounds as smooth as possible, and recognising when certain kick drums are just not gonna go with each other.

My advice for anybody who wants to experiment with harmonic mixing is to try to train your ear organically to mixing in key, and then use a tool like Mixed In Key to confirm how close or far you are away in the Camelot Wheel. I think that’s a good foundation and helps you to not become over reliant on it. Also note that the tool is not always 100% accurate.

Butch

“Your ears are always king in the end”

I play with four decks usually. I loop a lot, add vocals, melodies, textures, mix in samples, pads or other pieces of recorded music. For any DJ out there: to get so many different tracks to blend well together and to sound really good, you need harmonic mixing. To mix in the right key guarantees that I get clean mixes done, without interrupting the flow.

I use my eyes a lot because the display [on a CDJ] usually is right. It’s gotten really good, so that you can mostly rely on the analysis. (I use harmonic analysis in rekordbox.) But still, your ears are always king in the end. They are also what I fall back on, when I can’t find anything in the right key. Then I start only using my ears. I’m often happily surprised when I find that even though two tracks shouldn’t fit, they actually do. That often happens with minimal tracks. 

Train your ears. Recognising intervals, harmonies and note lengths is a skill you can develop and practice like any other. Also really good is frequency ear training, for producers especially. Just find an ear training software, download it and get busy practicing!

Are mixes that clash keys undesirable? No, you can’t rule anything out. Your ears are always king, and have to decide. Especially if you don’t know any music theory, you shouldn’t be put off, even if the keys shown aren’t the same. Tip: Learn the thirds and fifths in every key and then from there the other intervals as well. When you mix in a tune with a single-note bassline in the key a third of fifth or even sixth above the tune you are playing in, there can be really cool effects. It won’t always sound good, but learn some music theory and have fun playing around. 

DJ Puffy

“Dive right in! Experiment and have fun!”

I try not to complicate things, really. I try to imagine and sometimes even sing/hum the words or instruments of the potential blend or mix to myself (this can be a bit weird to my friends sometimes). It’s a more practical approach. Other times I would consider the track I’m mixing out of, search for that key in my DJ software, and go through a trial and error process.

I’ve always leaned more on trusting my ears a bit more. While the technology we use now is very advanced (I mostly use Serato and the DJM-S9 or -S11 when I’m mixing harmonically) it is important to still try things on your own. I’ve surprised myself a few times [laughs]. Lots of my homies mix in key. To them, it’s become almost second nature.

Mixes that clash keys are extremely undesirable! To me, it’s like you’re trying to jam a puzzle piece in a space it’s not meant for. Super cringe.

And any advice for people? Just try it! Also another thing to note would be that if someone is rapping or chanting there’s not necessarily a key associated with that. Keys count when considering the instruments or someone who is singing, but it’s still important to listen and determine yourself. Dive right in! Experiment and have fun! That’s the best way.