Music Theory (#229)
in [Ruby]
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From: Jean Lazarou on 8 Mar 2010 14:55 Here is a partial solution, it does not support all type of chord symbols (see comments in the main script). The main script is chord_translator.rb, it contains the 'chord' API and also translates chords when run from the command line. Usage: ruby chord_translator.rb {chord-symbols} Example: >ruby chord_translator.rb C Cdim7 Am F#+7 C => C E G Cdim7 => C Eb Gb A Am => A C E F#+7 => F# A# D E The chord_translator_test.rb file contain tests validating the currently supported chord symbols and also presents the APIs implemented by chord_translator.rb. The other scripts are files for the GUI version of the tool, they use the current trunk version of Swiby (a layer on top of Java/Swing) and need jRuby. (the first two scripts can run with any Ruby interpreter) The startup command is: jruby -I<swiby-trunk>/core/lib chord_translator_ui.rb (chord_translator_ui.rb contains the GUI definition and the GUI logic - pretty basic -, score_painter.rb paints the musical notation - staff - and styles.rb defines the CSS-like styles of the GUI). It uses a font to draw the musical symbols, downloaded from http://simplythebest.net/fonts/fonts/musical_symbols.html The attached ZIP-file contains all the scripts and an image file presenting a run of the GUI version. Regards to all... Attachments: http://www.ruby-forum.com/attachment/4551/chord.zip -- Posted via http://www.ruby-forum.com/.
From: Daniel Moore on 3 Apr 2010 13:25
Introduction *This summary was written by Jean Lazarou.* This quiz has some tricky aspects; translating a chord symbol to the notes that it comprise may be ambiguous. The rule to follow when interpreting a chord symbol may be different from one person to another and still be correct. As an example take the C major chord, one may expect three notes (C, E and G). On a guitar you can produce 6 notes, on a piano you can produce 10 notes. Would you only play three notes? Another example: Cb on the piano results in hitting the B key. Should a chord like Ab-Cb be rendered as Ab-B? Have a look at the thread of discussion Therefore, I am not considering all interpretation differences. I am not an expert and I would probably be wrong. Terminology In the hope to make the summary clear, lets first present the terminology we use. The thing the solution program expects as input is a chord symbol. The chord symbol has a specific syntax. It starts with a note name, a letter from A to G, that we name the chord root. We can assign a pitch to the note, a flat or a sharp. We write a flatted note by adding the lower case letter b and a sharped by adding the # symbol. After the root note follows the quality and the extension, they are a limited set of strings defining what notes to include in the produced chord |