Extentions

This script shows some of the extensions I have created for accessing (and writing) midi files.

Contents

Tracks

The standard note matrix from the Midi Toolbox. does not have track information. My extensions add an eighth column to the note matrix with track information.

% Read in a midi file an get the track information
nm = readmidi_java('202.kar',true);
fprintf('There are %d tracks with notes in this midi file.\n', ...
    length(unique(nm(:,8))));
% And write out tracks ...
writemidi_java(nm,'track_demo.mid');
% If we read this newly created midi file back in again, we should get the
% tracks...
nm_new = readmidi_java('track_demo.mid',true);
figure(1);
clf;
plot(nm(:,8) == nm_new(:,8),'b*');
title('Note track numbers check');
xlabel('note number');
ylim([-0.2 1.2]);
set(gca,'YTick',[0,1])
set(gca,'YTickLabel',{'different','same'})

There are 3 tracks with notes in this midi file.

Lyrics

Some midi files have lyrics embedded in them. If the file extension is .kar rather than .mid or .midi, it will almost certainly have lyrics.

% Get the lyrics in text form.  get_lyrics_as_bytes() will give you the raw
% bytes, which may be easier to use for more complex processing.  Some of
% the original lyric commands in the midi file may have unprintable
% characters.  These unprintable characters are converted into hex strings
% by get_lyrics_as_text().
[lyrics info] = get_lyrics_as_text('202.kar');

% Now go ahead and print out the first 20 lyric commands and their times in
% seconds
fprintf('********* FIRST 20 RAW LYRICS ********* \n\n');
for i=1:20
   fprintf('%g: |%s|\n',info(i,2),lyrics{i});
end
fprintf('\n\n');

% Now try to do something a little smarter so that we can see the lyrics
% as lines.  In this particular midi file, 0xd indicates and end of line
% and 0xa indicates a new stanza.
fprintf('********* LYRICS IN STANZAS ********* \n\n');
for i=1:length(lyrics)
    if strcmp(lyrics{i},'[0xd]')
        fprintf('\n');
    elseif strcmp(lyrics{i},'[0xa]')
        fprintf('\n');
    else
        fprintf('%s',lyrics{i});
    end
end

********* FIRST 20 RAW LYRICS ********* 

5.85938: |YUM.: The |
6.09375: |sun, |
6.32813: |whose |
6.5625: |rays |
6.5625: |[0xd]|
6.79688: |Are |
7.03125: |all |
7.26563: |a|
7.5: |blaze |
7.5: |[0xd]|
7.73438: |With |
7.96875: |ev|
8.20313: |er-|
8.4375: |li|
8.90625: |ving |
9.375: |glo|
10.3125: |ry, |
10.3125: |[0xd]|
11.4844: |Does |
11.7188: |not |


********* LYRICS IN STANZAS ********* 

YUM.: The sun, whose rays 
Are all ablaze 
With ever-living glory, 
Does not deny 
His majesty-- 
He scorns to tell a story! 
He don't exclaim, 
"I blush for shame, 
So kindly be indulgent." 
But, fierce and bold, 
In fiery gold, 
He glories all effulgent! 

I mean to rule the earth, 
As he the sky-- 
We really know our worth, 
The sun and I! 

I mean to rule the earth, 
As he the sky-- 
We really know our worth, 
The sun and I! 

Observe his flame, 
That placid dame, 
The moon's Celestial Highness; 
There's not a trace 
Upon her face 
Of diffidence or shyness: 
She borrows light 
That, through the night, 
Mankind may all acclaim her! 
And, truth to tell, 
She lights up well, 
So I, for one, don't blame her! 

Ah, pray make no mistake, 
We are not shy; 
We're very wide awake, 
The moon and I! 
Ah, pray make no mistake, 
We are not shy; 
We're very wide awake, 
The moon and I! 

Instrumentation

Program commands change the instrumentation for individual channels in tracks. Each patch number corresponds to a particular instrument. My extensions allow you to read the patch commands out of an existing midi file and they allow you to specify a single patch per channel per track when writing midi files. You can listen to the original midi file - with the extension changed to .mid - here and the midi file with trumpet vocals here. The vocals start about 6 seconds in.

% first get the note matrix with track information
nm = readmidi_java('202.kar',true);

% now get the program changes
changes = get_program_changes('202.kar');

% let's find out what the patch was for the vocal channel
vocal_patch = changes(changes(:,5) == 3,:);

% it's a piccolo, number 73
fprintf('Vocal patch #: %d\n', vocal_patch(1));

% now let's create a new .mid file where the vocals are on a trumpet (57)
writemidi_seconds(nm,'vocals_with_trumpet.mid',[3 vocal_patch(4) 57]);

Vocal patch #: 73

Tempos

Tempo commands change the lengths of beats. The note matrix returned by readmidi_java takes these tempo changes into account.

tempos = get_tempos('202.kar');
% There are quite a lot of these changes
figure(1);
clf;
plot(tempos(:,3), tempos(:,1),'*-');
title('Tempo changes in 202.kar');
xlabel('Time (s)');
ylabel('Beats per minute');
ylim([0 max(ylim)]);

% 2010-05-03 Christine Smit [email protected]
% Released under the GNU Public License v. 3

Published with MATLAB® 7.8