# Rockbox

## FS#2231 - Pitch adjustment in musical terms (for practicing musicians)

Attached to Project: Rockbox
Opened by Bruce Bertrand (brucebertrand) - Thursday, 17 June 2004, 04:41 GMT
Last edited by Rani Hod (RaeNye) - Wednesday, 20 September 2006, 23:07 GMT
Task Type Feature Requests Music playback Closed No-one All players Low Normal Undecided Undecided 0 No

### Details

For musicians who use the pitch adjustment feature for
practice (mostly with Jazz playalong's), adjusting the
pitch with the current method is not very useful.

A nice option would be to adjust the pitch by semitones
(or half steps).

To raise pitch in equally tempered half steps, use the
following equation:

F = (2^(1/(12/N))) * B

Where:
F = end frequency
B = starting frequency
N = # of half steps displaced (absolute value)

To lower pitch, divide, rather than multiply, by B

Is accurate enough math possible (and efficient) with
the archos (recorder)?

If not, you can use: F = B * 1.06^N

This method is only relatively accurate to about a
perfect 5th (7 half steps), which is OK. A perfect 5th
up plus a perfect 5th down gives you more than an
octave, and thus, covers all keys.

Also usefull, for those who would be thinking in
musical terms, is displaying the adjustment not by the
number of half steps (+4 , -2 , etc...) , but by
interval (M3 up, m2 down, etc...)

For reference, if whoever might implement this doesn't
have a musical background, a interval list follows:

1 = m2 (minor 2nd)
2 = M2 (Major 2nd)
3 = m3
4 = M3
5 = P4 (Perfect 4th)
6 = TT (Tritone)
7 = P5
8 = m6
9 = M6
10 = m7
11 = M7
12 = 8va (Octave)

Too bad there's not enough processing power to do this
without affecting the tempo.

TIA