Sunday, 15 April 2012 20:18

How To Use DJ Tools Featured

Written by  Pete Simpson
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DJ Tools iPhone App DJ Tools iPhone App Pete Simpson

DJ Tools is an iPhone app designed for working DJs. I wrote this app because I needed it, and I couldn't find equivalent on the app store. This app will help you to mark up your collection with BPM and key information, two critical aspects of any tune you will want to know if you're going to mix it with others....


This app will not tell you what key a tune is in automatically, it will not scan your iTunes folder and mark up tunes, or do anything similar. Myself, and others, have found the most complex algorithms incapable of finding the correct key with any accuracy. This app will help you identify the key of a tune by playing a chord in that key. You have to do the brain work, listen to the chords, compare and decide on the key yourself. Trust me, even if you're tone deaf, you're still infinitely better at identifying a song's key than a computer is. The BPM analysis is similar, and involves tapping the screen to the beat for a few seconds.

I designed this tool so I could play a tune, work out quickly the BPM and key, get the marker out, and mark up the label. Over all, this is designed for DJs, it will not make you a DJ by doing the hard bits for you, but it will enhance your arsenal, and offer some creative ways for  experienced DJs to fine-tune their art.

The following sections will describe the interface in more detail, give examples of how this tool can be applied to your sets to improve your mixes, and discuss the theory and the art of harmonic mixing.


This section is a quick guide for those who want to get working, and already understand the principal of harmonic mixing.

In the main interface, you will see an LCD style display and a set of buttons with musical keys on them. There are sixteen buttons, matching the eight major and eight minor keys.

Put a tune on your deck, and let it play. Pick something simple if you're unfamiliar with recognising musical keys. Tap the LCD screen to the beat, and you will see that after a few beats it will begin to display BPM information. The more times you tap, the more accurate the display will be.

Now we have the BPM, we need the key. Make sure the audio on your iPhone is on, then press any of the major key buttons. Is your iPhone playing the same key as the song? If not, try another, and work your way through them, major and minor, until you find it. It should be clear when you have it right.

Each time you select a key button, it will display the information on the screen. So, when you have the right key, check the display.

The display will now look similar to the image below.

LCD Display

From the results I can determine the following:

  • The BPM is 140
  • The key is D Minor
  • The key code is 7A
  • The track will mix harmonically with tracks in the keys A Minor,F, and G Minor
  • The track will mix harmonically with tracks in the key codes 8A, 7B and 6A

Key codes are a  representation of the key useful in this technique, and are described later in this tutorial.


The main screen of DJ Tools comprises of an LCD style display screen at the top, a set of buttons beneath, and a navigation bar at the bottom.

LCD Display



LCD Display

This displays information on key and BPM. It also functions as a button. The display will show

  • Key
    The key button that was last pressed
  • Code
    An alternate form of key information which is very useful for DJs. More later...
  • BPM
    The BPM tapped on the screen
  • Mix with key
    Other keys that will mix harmonically with this key
  • Mix with code
    Other codes that will mix harmonically with this code

Try tapping it in time for a few seconds, and it will display the BPM which you were tapping.

If you press one of the key buttons beneath the display, it will show information on that key and suitable keys that mix well with it.


The key buttons will trigger a piano chord in the key pressed. Try pressing a few to get the idea. To analyse the key of a song, listen to the song, and pick different keys. Most will sound discordant, some will sound OK but there's usually only one that will be the key of the song. Once you have it, the display shows you what will mix with it,  and what it's key code is.


This will display a white screen, so that the screen can be used as a light source when you need one. If you have an iPhone 4, it will also power the LED flash on the device.


Contains this help file


There is a lot of argument regarding harmonic mixing. You will hear similar arguments as the vinyl / CD / DAW debates, i.e. general noise and opinion, with little value to the individual other than to make you feel dumb. All I will say is this: If you play two discordant tunes at the same time, you and your audience will know about it!

Harmonic mixing is a technique that all DJs use, they may not be aware of the specifics, but they know what sounds right. Working out the keys to all your tracks before you start mixing them is very useful, the more information you have, the quicker you can get tracks into your sets. I find it gives me ideas for great mixes I may not otherwise have considered.

If you know that two songs share the same key, for example A Minor, they will mix together and be in tune with each other. All the notes should be of the same scale. The problem comes when you realise there are many possible scales. Some mix well, others sound like there's a cat on the keyboard. There's quite a science behind why some things sound harmonious and others do not. This is where music theory comes in.


The concepts of harmonic musical combination for this technique come from a superbly useful music theory diagram, the circle of Fifths.

Circle Of Fifths

It shows the relationship between the twelve tones of the chromatic scale, their corresponding key signatures, and the associated major and minor keys. For more detail check out this tutorial. The great thing about this diagram is that keys adjacent to other keys have very similar notes in them. By moving in, out, clockwise, or anticlockwise from a root key, those keys will mix with the root key with the minimum of discordant notes. If my tutorial wasn't detailed enough, check out this wiki article.


The diagram above is customised for DJ use. I've included on it a commonly used code that makes this technique much easier to implement while learning the circle of fifths. You either have to memorise that diagram, or use codes to represent the keys which remove the need for the diagram.

Using the codes, you can see that if it's the same key , one number higher or lower, or the same number but a different letter, then it will mix harmonically.

Circle Of Fifths Highlighted

Check the diagram, you will see what I mean. If I had a song in F-Sharp Minor (F#m) it would mix harmonically with songs in C Sharp Minor (Cm), B Minor (Bm), or A Major (A). So if you look at the key codes, if I had a track marked 11A it would mix well with 10A, 12A, and 11B.

As a general rule, stepping up the numbers is preferable. So, a set may be constructed like so:

5B - track 1
5B - track 2
5A - track 3
6A - track 4
6A - track 5
7A - track 6

The keys enable you to choose tunes that match harmonically just by knowing the key codes, without reference to the diagram.

I would recommend labelling your tracks with both. The codes are a quick, simple method to utilise the circle of fifths and ensure harmonic cohesion, but if you always see both, then you will learn the scales accidentally, and from there you can start to understand other methods of harmonic mixing. Here's a hint, if you shift the key by a tone, it can lift the energy of the dance floor. Such a technique can be repeated to give a feeling that the music just climbing and climbing. Clearly this is a good thing to do when you are trying to energise a crowd. To do this with the codes you have to add seven to the number (rolling from twelve to one, like a clock).

Start with the codes, learn both codes and keys, work on learning the circle, and think about what else you might find, when all this is second nature to you.

Read 51041 times Last modified on Wednesday, 18 April 2012 18:17
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