If you really want to progress your mixing to the next level, then learning to mix in key is the obvious next step. If you listen to a DJ in a club, or on a mix CD, it’s this that makes the difference between a mix that’s merely okay, and a mix that makes you sit back and say “wow, that’s amazing”.

But what is mixing in key, exactly? Basically, it’s the art of choosing your records so that not only do the beats match up, but the musical elements are in harmony also. All records are in a certain key, whether it’s A, C, G or whatever, and there are certain other keys that will go with those keys and others that won’t. So mixing in key is all about knowing which is which! It’s not, I should point out right now, about only playing records that are in the same key all night: do that and you’d soon find you had a pretty narrow repertoire to choose from!

The way round it is this. When you’re making music on a keyboard, if you play a chord, you get three notes around the one key. So when you have a three-note chord, that gives you the three options: the key and two other keys you can mix with that one key that will all work. And then you start getting harmonies, basically, and that’s how you start playing other records that are in harmony, without necessarily staying in the same key.

The first thing you have to do, though, is work out what key a record is in in the first place. And that’s not something I can really tell you how to do now: you need to know a little bit about making music before you’ll get this one! So while I, for instance, can’t actually play the piano, I do know what notes make up what chords, and that gives you the keys you can work with. So for instance, G minor will mix with G, C and D minor, and the relative major would be B flat.

Not that I’m a geek but…

What I personally do is mark my records with a label saying what key they’re in. I’ve got over 20,000 records at home, and each and every one of them is marked with both the key it’s in, and the BPMs.

That way, my brain is freed to work creatively in the mix: I’m not scrabbling about in my box thinking, will this go with this? Now to be honest, knowing what will go with what is something that most DJs pick up instinctively over time anyway, but there’s two advantages to using this method. Firstly, it’s fool-proof: it takes all the guesswork out of it. If you think two things will go together and they don’t, and you’re playing in a club, then it’s already too late: half the club has already turned round and gone, ‘eurgh’. So doing it this way is safer.

Secondly, I don’t get a lot of time to practise between gigs at home: I’m playing four or five nights a week, and I’m getting sent new records every day. So keying my records is a good guide for me to play a live set without any practice, but still sound as professional as possible. It means I can mix together two records I’ve only heard a couple of times, and still be sure I’m not going to end up with horribly clashing basslines!

The other thing you have to bear in mind if you’re going to try this is that using the pitch control will of course affect what key the record is in. I’m not quite sure of the mathematics of it all, but as a rule of thumb, each time you raise or lower the pitch by 4 or 4.5 per cent, you’ll raise or lower the key by a semitone. So a record that’s in the key of G when played at the zero, ‘green light’ position, will be in the key of A flat if you pitch it up to plus four.

Mixing in key does seem to be particularly popular among the progressive house fraternity, admittedly, but it’s a skill that can be applied to all genres of music. After all, there are very few records that consist entirely of drumbeats! For instance, I’ve got plenty of drum & bass records that have some lovely warm pads and swirling synths: work out what key those are in and you can pull off some fantastic mixes. You know when you hear these mix CDs and you think, that goes so well, how does he do it? Well, now you know the answer!