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gmuller/midi2freq.c

Created March 3, 2011 15:15
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  1. gmuller created this gist Mar 3, 2011.
    16 changes: 16 additions & 0 deletions midi2freq.c
    View file
    Original file line number Diff line number Diff line change
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    #include <stdio.h>
    #include <math.h>

    int main(){
    double semitone_ratio, c0, c5, frequency, fracmidi;
    int midinote = 73;

    semitone_ratio = pow(2, 1/12.0);
    c5 = 220.0 * pow(semitone_ratio, 3);
    c0 = c5 * pow(0.5, 5);

    frequency = c0 * pow(semitone_ratio, midinote);
    //and in reverse
    fracmidi = log(frequency / c0) / log(semitone_ratio);
    midinote = ( int)(fracmidi + 0.5);
    }