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#!/usr/bin/perl -w
sub usage {
die <<EOF;
Usage: $0 [-annn] note
Where `note' is a letter A through F, with optional # or b (sharp
or flat), followed by an octave number (e.g. A4 is a concert A, E1 is
the low E on a bass, E2 is the low E on a guitar, C4 is "middle C").
Frequencies are by default calculated using "concert pitch", where A4 = 440Hz.
If -annn option is given, the "nnn" will be used as the pitch of A4 instead.
(In other words, "-a440" is the default).
EOF
}
%notes = (
C => 1,
'C#' => 2,
Db => 2,
D => 3,
'D#' => 4,
Eb => 4,
E => 5,
F => 6,
'F#' => 7,
Gb => 7,
G => 8,
'G#' => 9,
Ab => 9,
A => 10,
'A#' => 11,
Bb => 11,
B => 12
);
if(@ARGV && ($ARGV[0] =~ /^-a([.\d]+)$/)) {
$ref = $1;
shift;
} else {
$ref = 440; # A440
}
$refnum = $notes{A} + 12*4;
$_ = shift;
($note, $oct) = /^([A-G][#b]?)-?(\d\d?)/i;
usage unless $note;
$num = $notes{ucfirst lc $note} + (12*$oct) - $refnum;
$freq = $ref * (2 ** ($num/12));
print "$freq\n";
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