[linux-audio-user] transposing frequency

[Cesare Marilungo]

Atte André Jensen wrote:

> Hi
>
> Suppose I have an A with a frequency of 440 hz. Which formula should I 
> use for transposing x semitones up/down? So which frequency would the 
> Bb a half step higher for instance have? What about cents (1/100's of 
> half steps)?
>
You know that every note has a frequency which is twice the frequency of 
the same note an octave below. You have too go from the A at 440 hz to 
the A at 880 hz with 12 equal steps. So, for each semitone you have to 
multiply the frequency of the previous note by the twelfth root of two 
(approx. 1.059463094).

See:
http://en.wikipedia.org/wiki/Twelfth_root_of_two

c
www.cesaremarilungo.com