www.pudn.com > midi2frq.rar > midi2frq.m

function f=midi2frq(n,s) 
%MIDI2FRQ	Convert musical note numbers to frequencies F=(N,S) 
%		s is:	'e' equal tempered (default) 
%			'p' pythagorean scale 
%			'j' just intonation 
% 
% notes are numbered in semitones with middle C being 60 
% On the equal tempered scale, note 69 (the A above middle C) 
% has a frequency of 440 Hz. 
% 
% see FRQ2NOTE for the inverse transform 
 
% Pythagorean 
%     sharps 1 2187/2048 9/8 19683/16384 81/64 4/3 729/512  3/2 6561/4096 27/16 59049/32768 243/128 2 
%     flats  1 256/243   9/8 32/27       81/64 4/3 1024/729 3/2 128/81    27/16 16/9        243/128 2 
% 
% Just Intonation 
%     sharps 1 25/24 9/8 75/64 5/4 4/3 45/32  3/2 25/16 5/3 225/128 15/8 2 
%     flats  1 16/15 9/8 6/5   5/4 4/3 108/75 3/2 8/5   5/3 18/10   15/8 2 
 
 
%      Copyright (C) Mike Brookes 1997 
%      Version: $Id: midi2frq.m,v 1.3 2005/02/21 15:22:13 dmb Exp $ 
% 
%   VOICEBOX is a MATLAB toolbox for speech processing. 
%   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 
% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
%   This program is free software; you can redistribute it and/or modify 
%   it under the terms of the GNU General Public License as published by 
%   the Free Software Foundation; either version 2 of the License, or 
%   (at your option) any later version. 
% 
%   This program is distributed in the hope that it will be useful, 
%   but WITHOUT ANY WARRANTY; without even the implied warranty of 
%   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
%   GNU General Public License for more details. 
% 
%   You can obtain a copy of the GNU General Public License from 
%   ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to 
%   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
if nargin > 1 
  if s(1)=='p' 
    r=[256/243 9/8 32/27 81/64 4/3 729/512 3/2 128/81 27/16 16/9 243/128]; 
  elseif s(1)=='j' 
    r=[16/15 9/8 6/5 5/4 4/3 36/25 3/2 8/5 5/3 9/5 15/8]; 
  else 
    r=0; 
  end 
  if r(1) 
    c=[0 0 12*log(r)/log(2)-(1:11) 0]; 
    nm=mod(n,12); 
    na=floor(nm); 
    nb=nm-na; 
    f=440*exp((n+c(na+2).*(1-nb)+c(na+3).*nb-69)*log(2)/12); 
  else 
    f=440*exp((n-69)*log(2)/12); 
  end 
else 
  f=440*exp((n-69)*log(2)/12); 
end