old_contents: // Load the markdown-it regex plugin
  const mdRegex = require('markdown-it-regexp')
  
  // Set our chord's identifier regex pattern and replacement string
  const chordPattern = mdRegex(
    // regexp to match
    // Assuming anything within square brackets to be a chord
    /\[(\w+)\]/,
  
    // this function will be called when something's in square brackets
    function(match, utils) {
      return '<span class="chord"><span class="inner">' + match[1] + '</span></span>';
    }
  )
  
  // Import markdown-it and configure it to use our chordpattern
  const md = require('markdown-it')({
    html:         false,        // Enable HTML tags in source
    xhtmlOut:     true,         // Use '/' to close single tags (<br />).
                                // This is only for full CommonMark compatibility.
    breaks:       true,         // Convert '\n' in paragraphs into <br>
    linkify:      true,         // Autoconvert URL-like text to links
  
    // Enable some language-neutral replacement + quotes beautification
    typographer:  false,
  
    // Double + single quotes replacement pairs, when typographer enabled,
    // and smartquotes on. Could be either a String or an Array.
    quotes: '“”‘’'
  }).use(chordPattern)
  
  
  module.exports = {
  
    // Our exported function
    toHtml: function (chordMarkdownText) {
      if(chordMarkdownText === undefined) {
        throw new Error('Argument chordMarkdownText is required.');
      }
      return md.render(chordMarkdownText)
    }
  
  }
  
new_contents: // Load the markdown-it regex plugin
  const mdRegex = require('markdown-it-regexp')
  
  // Set our chord's identifier regex pattern and replacement string
  const chordPattern = mdRegex(
    // regexp to match
    // Assuming anything within square brackets to be a chord
    /\[[A-G](#|b|m|M|7|9|11|13|\(|\)|add|sub|dim|aug|maj|min)*(\/[A-G]#?b?)?\]/,
  
    // this function will be called when something's in square brackets
    function(match, utils) {
      return '<span class="chord"><span class="inner">' + match[1] + '</span></span>';
    }
  )
  
  // Import markdown-it and configure it to use our chordpattern
  const md = require('markdown-it')({
    html:         false,        // Enable HTML tags in source
    xhtmlOut:     true,         // Use '/' to close single tags (<br />).
                                // This is only for full CommonMark compatibility.
    breaks:       true,         // Convert '\n' in paragraphs into <br>
    linkify:      true,         // Autoconvert URL-like text to links
  
    // Enable some language-neutral replacement + quotes beautification
    typographer:  false,
  
    // Double + single quotes replacement pairs, when typographer enabled,
    // and smartquotes on. Could be either a String or an Array.
    quotes: '“”‘’'
  }).use(chordPattern)
  
  
  module.exports = {
  
    // Our exported function
    toHtml: function (chordMarkdownText) {
      if(chordMarkdownText === undefined) {
        throw new Error('Argument chordMarkdownText is required.');
      }
      return md.render(chordMarkdownText)
    }
  
  }
  
subject: Improve the chord matching regex