Beat-mixing skills are the foundation of any great DJ. Subtract the ability to beat-match songs, and you are nothing more than a human jukebox. But as most experienced DJs know, beat mixing involves more than just matching beats. Some songs simply sound great together; other songs, even if their tempos are matched, just don't blend. If you create a great-sounding mix, it probably means that the blended songs are in a matching or harmonically complementary key.
UNLOCK THE KEY
As you know, beat mixing can be defined as a transition from one song to another with no noticeable gap in the audio signal. Beat mixes are generally performed by matching the tempo, calculated by noting the track's bpm, of the incoming record with that of the current record (or vice versa) and then synchronizing their beats as you fade up the incoming song and fade out the outgoing song. If the mix sounds good, perhaps you got lucky and found two songs that work well together. However, there's a good chance that they simply don't mix well, even if their tempos are perfectly matched and their beats are in sync. Here, the concept of harmonic mixing comes into play.
Every song, of course, has a key. Typically, this is defined by the song's bass line. If you mix during a percussion-only section of a song, the key can be ignored. However, if some melodic elements are playing and you want to combine them with the melody of the incoming song, you will need to know each track's key, or things simply won't sound right.
Put another way, if you blend two songs of similar tempos that have the same key, it should sound good because the melodies will be based on the same group of notes. If your turntable or CD player has a traditional pitch control, be aware that adjusting the pitch affects the key, especially if you adjust greater than ±3 percent. Some newer turntables and players include tempo-adjust or pitch-locking features with which they digitally process the file to maintain the same key while still letting you adjust the tempo. If your equipment includes this feature, adjusting the fader with it enabled will allow you to mix songs with larger differences in tempo.
Because playing songs in the same key all night long is limiting, the next step is to make transitions to songs of different keys. To do this, you need to know both the key of your songs and which keys are harmonically compatible. If music theory isn't your strong suit (it certainly wasn't mine) or you aren't blessed with perfect pitch, neither of these may be immediately apparent.
For detecting the key of a song, you can use the computer-based DJ program MixMeister Pro 6, by MixMeister Technology, or a plug-in such as Waves UltraPitch, both of which detect the key for you with reasonable levels of accuracy. You might also be able to find the keys of some of your songs online through some creative searching and message-board scouring.
With respect to the harmonic compatibility of keys, I recently discovered the Website Harmonic-Mixing.com (www.harmonic-mixing.com). Run by the company Camelot Sound, the Website presents tons of information about the concept of harmonic mixing and provides the Harmonic Keys Overlay Chart, which lists compatible keys in a table format. According to Camelot Sound founder Mark Davis, Stuart Soroka introduced the concept of harmonic keys to the DJ world in 1986 through a monthly DJ magazine. When the magazine folded in 1988, Davis continued to record the keys of his favorite tracks and made the information available to the DJ community. He also began the development of the Camelot Sound Easymix System as a means of simplifying the complexity of the key-based system.
With the Easymix System, each key is assigned a keycode and placed in the Harmonic Mixing-Wheel; adjacent keycodes are harmonically compatible. The keycodes are numbered from 1 to 12 (with major keys assigned a B and minor keys an A). The system is designed such that you can select songs with numerically adjacent keycodes and be confident that they are harmonically compatible.
Camelot Sound offers subscription and pay-as-you-go services that give you access to its database of more than 33,000 songs for which keycodes have been recorded. Users can purchase the entire list or sign up for an annual subscription that includes the complete list as well as monthly updates (more than 100 new songs are added each month). If you are a professional DJ (or aim to be), this could be money well spent.
Understanding what makes two songs mix well together is a valuable skill for any DJ. With the help of the Harmonic Keys Overlay Chart, the Harmonic Mixing-Wheel and the keycode system, you can better plan your sets. If taking your DJ performances to the next level is appealing to you, I recommend reading more about the concept of harmonic mixing — you may also want to begin marking your records with the keycode in addition to the bpm. Even if you don't formally use the harmonic-mixing information provided here, you should now have a better understanding of what makes certain songs compatible.