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How To: Understanding key and tempo in Harmonic Mixing
Overview
Harmonic mixing is based on the idea of mixing harmonically-compatible songs. The standard approach is to detect root notes at the song’s original tempo and find other compatible songs that will fit. This technique is used by thousands of professional DJs.
However, it is important to understand that changing the tempo of the song will change the key as well. Even the smallest tempo change will alter the key, but a 6% difference will change the key to a whole new one.
6% Rule
6% is thus the magic number: it will move your song to the adjacent key on the piano, as illustrated below:
If your original song was recorded in F Minor, increasing the tempo by 6% will move the song one key to the right to give you G-Flat Minor.
This is equivalent to adding 7 to your current Camelot number. Since F Minor has an equivalent keycode of 4A, adding 7 will give you the result of 11A. The piano roll above shows you that 11A is indeed equivalent to Gbm.
Decreasing the tempo by 6% has the reverse effect: It moves your song one key to the left, or the equivalent to subtracting 7 from your current Camelot number. This is illustrated below:
3% Rule
There is a basic rule for smaller increments: If you change the tempo by less than 3%, keep your original key. If you change the tempo by 3% or more, use the 6% key.
It works in this way because 3% the middle point. Anything below 3% will be closer to your original key (F Minor) and anything above 3% will be closer to your 6% key (Gb minor or E minor, depending whether you increase or decrease the tempo).
Examples
Two songs in F Minor that have roughly the same BPMs: 130 and 131. We can harmonically mix them together because the tempo difference is less than 3%.
Next up are two songs in A Minor with different tempos. First song is 128 BPM and the second is 136 BPM. To beatmatch the slower song with the faster song, we’ll have to increase its tempo by exactly 6.25%. This will move the slower song one key to the right, making it B-flat Minor rather than A Minor. The new keys will no longer result in a harmonic mix because A Minor (8A) and B-Flat Minor (3A) are not compatible Camelot numbers.
Using “Master Tempo”
If your DJ equipment or software supports “Master Tempo,” use it! Master Tempo is a pitch-correction technique that makes it easy to use harmonic mixing at any tempo. If you increase the tempo of an A Minor song by 6.25%, your “Master Tempo” button will keep the song in A Minor.
Conclusion
In summary, if your tempo change is less than 3%, use the original key. If your tempo is greater than 3%, use the 6% key. The new +6% key can be figured out by adding 7 to your current Camelot code. The new -6% key can be figured out by subtracting 7 from your current Camelot code.
Understanding the relation between changing tempos and changing keys can help move your harmonic mixing to the next level.
For more How-To tutorials on Harmonic Mixing, check out http://www.MixedInKey.com/HowTo.aspx or Wikipedia entry at http://en.wikipedia.org/wiki/Harmonic_mixing
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