<?xml version="1.0" encoding="utf-16"?>
<ChordType name="C Minor" priority="Important">
  <description>C minor</description>
  <abbreviations>
    <abbr category="General">m</abbr>
    <abbr category="Jazz">-</abbr>
    <abbr category="Full">min</abbr>
  </abbreviations>
  <intervals>
    <interval quality="Perfect" number="Unison" />
    <interval quality="Minor" number="Third" />
    <interval quality="Perfect" number="Fifth" />
  </intervals>
</ChordType>

    public void ReadXml(XmlReader reader)
    {
      _Name = reader.GetAttribute("name");
      _Priority = (ChordTypePriority)Enum.Parse(typeof(ChordTypePriority), reader.GetAttribute("priority"));
      if (reader.ReadToFollowing("description"))
        _Description = reader.ReadElementContentAsString();

      if (reader.Name != "abbreviations")
        throw new InvalidOperationException("Abbreviations element missing.");
      if (!reader.ReadToDescendant("abbr"))
        throw new InvalidOperationException("At least one abbreviation element is required.");
      var abbreviations = new List<ChordTypeAbbreviation>();
      do
      {
        var abbr = new ChordTypeAbbreviation(
          category: reader.GetAttribute("category"),
          abbreviation: reader.ReadElementContentAsString()
          );

        abbreviations.Add(abbr);
      } while (reader.ReadToNextSibling("abbr"));
      _Abbreviations = abbreviations.ToArray();

      if (!reader.ReadToFollowing("intervals"))
        //here's where the code fails
        throw new InvalidOperationException("Intervals element missing.");
      var intervals = new List<Interval>();
      do
      {
        var interval = new Interval(reader.GetAttribute("quality"), reader.GetAttribute("number"));
        intervals.Add(interval);
      } while (reader.ReadToNextSibling("interval"));
      _Intervals = intervals.ToArray();
    }