💾 Archived View for thrig.me › blog › 2023 › 08 › 11 › midiwarble.pl captured on 2023-09-08 at 17:06:59.
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#!/usr/bin/env perl
# midiwarble - how does the pitch_wheel_change thing even work? map a
# sin() function to pitch_wheel_change events so that the effect can be
# heard and different devices tested. the actual message splits the
# value across two bytes, and some devices may only use some portion of
# those bytes
use 5.36.0;
use Getopt::Long 'GetOptions';
use Math::Trig ':pi';
use MIDI;
# ranges for some of these are detailed in the MIDI::Event docs. the
# patch should be instruments that sustain (woodwinds, strings) and
# probably not the wood block or snare drum
#
# things to check here include how small can range be before you can't
# hear the changes, what happens as you maximize the range, what
# different patch sound like, what happens when the step is tiny but the
# range very large, etc
my $chan = 0; # MIDI channel
my $circle = 12; # how many $step to complete a circle
my $midinum = 69; # A note
my $patch = 16; # drawbar organ
my $range = 1000; # -8192 .. 8191, though see the MIDI docs
my $repeat = 3; # how many times to go through a circle
my $step = 24; # MIDI dtime between wheel change events
my $ticks = 96; # some MIDI thing
my $velocity = 120; # pretty loud
GetOptions(
'circle=i' => \$circle,
'channel=i' => \$chan,
'patch=i' => \$patch,
'pitch=i' => \$midinum,
'range=i' => \$range,
'step=i' => \$step,
'ticks=i' => \$ticks,
'velocity=i' => \$velocity,
) or exit 64;
my $file = shift // 'out.midi';
my @events = (
[ 'patch_change', 0, $chan, $patch ],
[ 'note_on', 0, $chan, $midinum, $velocity ]
);
my $when = 0;
my $whole = $step * $circle;
my $max = $whole * $repeat;
while ( $when <= $max ) {
my $wheel = $range * sin( $when * pi2 / $whole );
# timidity shows text_event so those may be good to mark when the
# wheel is what, but fluidsynth (or at least my wrapper for it) does
# not show those
push @events, [ 'pitch_wheel_change', $step, $chan, $wheel ];
$when += $step;
}
push @events, [ 'note_off', $step, $chan, $midinum, 0 ];
MIDI::Opus->new(
{ format => 0,
ticks => $ticks,
tracks => [ MIDI::Track->new( { events => \@events } ) ]
}
)->write_to_file($file);