Most DJs have developed an ear for music, and when listening to a song or mix that is off-key, a mental alarm is triggered and it will sound noticably sour or unpleasant.
Most DJs will ride beat-mixes for more than a few bars, but they don't often ride them for very long, because the same mental alarm activates when the melodies and harmonies start to overlay. At this point a DJ has 3 choices: forget riding melody segments and use only percussion segments, overlay incompatible key segments and suffer the results, or mix harmonically by selecting compatible key segments.
Many advanced DJs already mix harmonically by a hit or miss method, although they may not know it. They already spend extra time to test potential mixes, and only use those which pass. By applying harmonic music theory and intelligently selecting songs, a DJ can eliminate countless hours of wasted test mixing.
Furthermore, by utilizing a tool such as Rapid Evolution a DJ can keep track of which songs work well together to make perfect mixes. Finding and remembering classic mixes has never been easier!
A song will be harmonically compatible if it is in:
For example, a song in Cm is compatible with other songs in Cm, its relative major D#/Eb, its subdominant Fm and its dominant Gm. Subdominant and dominant keys are easy to find because they are the 4th and 5th scale notes from the tonic note. Relative majors are 3 half-steps above the tonic note of the minor key (in this case, C to D#/Eb). Conversely, relative minors are 3 half-steps below the major's tonic note.
Furthermore, a song will be reasonably harmonically compatible if it is in:
In Rapid Evolution, enabling the option to “Ignore Major/Minor differences” has the effect of including these reasonable matches in key searches.
When matching songs harmonically, you must be aware that changing the speed of a song also changes its key, unless a key controller is used. To be exact, a 5.94631% shift in speed will shift the key by a half-step. So if you're mixing a song in Cm at +6%, it's going to be in C#m/Ebm. Similarly, a change in RPM on your turntable from 33 to 45 will shift the key up 5 half-steps, from Cm to Fm.
The following table summarizes the compatibility rules for Major keys:
|Key||Tonic||Perfect 4th (Sub-Dominant)||Perfect 5th (Dominant)||Relative Minor|
|C Major||C Major||F Major||G Major||A Minor|
|C#/Db Major||C#/Db Major||F#/Gb Major||G#/Ab Major||A#/Bb Minor|
|D Major||D Major||G Major||A Major||B Minor|
|D#/Eb Major||D#/Eb Major||G#/Ab Major||A#/Bb Major||C Minor|
|E Major||E Major||A Major||B Major||C#/Db Minor|
|F Major||F Major||A#/Bb Major||C Major||D Minor|
|F#/Gb Major||F#/Gb Major||B Major||C#/Db Major||D#/Eb Minor|
|G Major||G Major||C Major||D Major||E Minor|
|G#/Ab Major||G#/Ab Major||C#/Db Major||D#/Eb Major||F Minor|
|A Major||A Major||D Major||E Major||F#/Gb Minor|
|A#/#Bb Major||A#/Bb Major||D#/Eb Major||F Major||G Minor|
|B Major||B Major||E Major||F#/Gb Major||G#/Ab Minor|
|This key||…mixes perfectly with these keys…|
The following table summarizes the compatibility rules for Minor keys:
|Key||Tonic||Perfect Fourth (Sub-Dominant)||Perfect Fifth (Dominant)||Relative Major|
|C Minor||C Minor||F Minor||G Minor||D#/Eb Major|
|C#/Db Minor||C#/Db Minor||F#/Gb Minor||G#/Ab Minor||E Major|
|D Minor||D Minor||G Minor||A Minor||F Major|
|D#/Eb Minor||D#/Eb Minor||G#/Ab Minor||A#/Bb Minor||F#/Gb Major|
|E Minor||E Minor||A Minor||B Minor||G Major|
|F Minor||F Minor||A#/Bb Minor||C Minor||G#/Ab Major|
|F#/Gb Minor||F#/Gb Minor||B Minor||C#/Db Minor||A Major|
|G Minor||G Minor||C Minor||D Minor||A#/Bb Major|
|G#/Ab Minor||G#/Ab Minor||C#/Db Minor||D#/Eb Minor||B Major|
|A Minor||A Minor||D Minor||E Minor||C Major|
|A#/Bb Minor||A#/Bb Minor||D#/Eb Minor||F Minor||C#/Db Major|
|B Minor||B Minor||E Minor||F#/Gb Minor||D Major|
|This key||…mixes perfectly with these keys…|
A system of key codes was developed by Camelot Sound called “EasyMix” which makes this easier to remember. It assigns a code to each major and minor key based on the circle of fifths. From the chart below, you will see Cm is 5A. When working with key codes, compatible keys will always be +/- 1 number, or with the same number and a different letter. For example, 5A is compatible with 4A/6A and 5B, which corresponds to Fm/Gm and D#/Eb.
It is important to realize that the EasyMix system is a simplified view of harmonic mixing, and assumes the compared songs are at the same BPM. In reality each song is at a different BPM, and in altering the speeds of the songs to beat match them the keys will inevitably change, and the system can quickly become more complicated. For example, a song in 3A played at +6% bpm shift is not 4A, but 10A (+7 key codes).
Here are some more advanced techniques of harmonic mixing:
As stated previously, if you increase the speed of a song by about 6%, you also shift the song's key up to the next higher key on the chromatic scale (technically a half-step or semi-tone shift). Your keycode shifts up by 7 numbers. If you shift it up only 3%, you are half way to the next key (a hemi-tone shift). A song in G#/Ab Minor (1A) shifts to A Minor (8A) with a 6% increase in speed. A song in D#/Eb Minor (2A) becomes an E Minor (9A) song with a 6% increase. The tempo of a song is irrelevant when applying this rule, because the audio frequency of any tone is unaffected by how often it is played.
Using the preceding theory, you can make radical shifts from one key region to another while still mixing harmonically.
A modulation mix provides exciting results by jumping a half step or whole step on the chromatic scale without significant changes in speed. For example, a half step jump (7 keycodes) may be from D#/Eb Minor (2A) to E Minor (9A). A whole step jump (2 keycodes) may be from D#/Eb Minor to F Minor. This type of mix can give quite a tangible lift to the energy on your floor. Do NOT attempt to overlay the melodic elements (such as the bass lines) in modulation mixes, only percussion segments of one source, otherwise the sounds will clash. Make sure the mix is complete when the new bassline/melody starts. Following the same procedures you can also modulate from a minor to a major key, or vice versa.
This is essentially using the modulation technique above to go up 1 or 2 half steps in the chromatic scale. This will inject quite a large amount of energy onto a dance floor if done correctly. Try a quick change in bassline.
You can constantly change the key and remain harmonically compatible by mixing up or down the circle of 5ths. To do this, you would select songs that are the Perfect 4th or 5th relative to the current key. In doing this, you will eventually cycle through all 12 Major or Minor keys arriving full circle at the original key.
For example, G → D → A → E → B → F#/Gb → C#/Db → G#/Ab → D#/Eb → A#/Bb → F → C → G.
The use of key controllers allows the key of a song to remain constant when the speed is changed. It has been referred to as key lock, pitch lock and master tempo. Not only does this increase the number of songs that can be made compatible, but it removes unwanted, audible changes to the pitch of a song when the speed is abruptly changed (perhaps due to beat matching). While introducing key controller further complicates the rules of harmonic mixing, Rapid Evolution can easily tell you whether to use key lock or not to make 2 songs compatible.
Advanced key controllers enable you to alter the key of a song during performance. This can enable any songs to be made in key! However, changing a song's key generally has negative side effects on the quality of the sound. It is preferable to match keys using naturally compatible songs as opposed to forcing key changes electronically. If you must change the song's key, try to change it as little as possible to minimize distortion. Rapid Evolution can be configured to display the minimal pitch shift (after beat matching) to make any 2 songs compatible.
There are different scales called “modes” which can be constructed by looking at the intervals between white notes on the keyboard (see Advanced Theory). These modes are all related and if the modes of your songs are known, you can find harmonically compatible matches that are not predicted by the keycode system above.
First of all, it is convenient to see the different modes as being variations of the normal major and minor scales.
Generally speaking, different major and minor modes with the same tonic note will be compatible. For example, D major ionian and D major lydian will sound well together, as they only share 1 different note.
There exists even more harmonic matches when you realize each mode has a relative in another mode which shares the same notes. For example, the following modes all share the same scale notes (in this case, all white notes):
Notice: C major and it's relative A minor are really just compatible modes!
By utilizing this knowledge, you can look for compatible songs by finding songs in a compatible mode. For example, D# minor (2A) and F minor (4A) normally are not compatible (according to the Camelot system above). However, D# minor dorian and F minor phrygian actually share the same scale notes (although different tonal centers), and would be a reasonable harmonic match.
With respect to the key code system, these modes have the effect of raising or lowering the logical key code by 1, in this manner:
Using the example above, a song in D# minor (2A) of the dorian mode is more similar to A# minor (3A), and conversely, the song in F minor (4A) of the phrygian mode is also more similar to A# minor (3A), thus they are compatible.
To demonstrate the opposite, C major and F major are normally compatible. However, C major lydian, due to the raised 4th (F# instead of F), would definitely clash with F major.
As you can see, knowing the exact modes of your songs can reveal more harmonic opportunities, and also reveal why some compatible matches might be more sour than you'd think. This advanced theory will soon be incorporated into the “key search” functionality in Rapid Evolution, and has already been built into the key detection algorithm.