Changing the Key of a track in Traktor?

[Siddy]

Sorry to dig up this old thread, but I just googled Key Change in Traktor and this thread was the most helpful and I saw this unanswered question.

Does anyone know the math/science behind this, and want to explain this a little?

I would love to know the underlying science here.

The difference between a key/scale is doubling or halving the frequency.
Increasing an octave (say, from C1 to C2) is doubling.
Decreasing an octave (say from C2 to C1) is halving.
And the difference between notes is a discrete increment change in frequency. between an octave, the frequencies have been split into 12 notes, this is arbitrary and is just what what determined a long time ago.
There is a very large number of discrete frequencies between what we call an octave, so much so that it bending the pitch of an instrument sounds continuous (but cant be continuous in accordance with modern particle physics).

Traktor is doing that when it changes the Key BUT if it did it simply by changing the frequency then the track would also increase/decrease in length (ie, pitch control).
So to achieve constant tempo/bpm with change in key (or change in temp with a cosntant key, ie Key Lock) the sound wave has to oscillate between the new frequency and blank space, so as to maintain the overall time taken for the waves to be produced - they are crammed into or drawn out the same space.

I don't work for NI so I don't know exactly how they do that, but you can check youtube physics lectures on waves that show how it works.

[Nicky H]

Why would you want to change the key of a song that someone has spent ages making???

Play it as it should be played - if its too slow/fast play something else...

LISTEN to your songs ffs

Beatgrid, sync, key, what next - little Jesus dolls doing it for ya