 
 extension ChordType: CustomStringConvertible {
 
+  /// Converts `ChordType` to string with its name.
   public var description: String {
     switch self {
     case .maj: return "maj"

  /// Eighth note.
  case eighth
  /// Sixteenth note.
  case sixtenth
  /// Thirtysecond note.
  case thirtysecond
  /// Sixtyfourth note.


/// Chord object with its type and key.
public struct Chord {
  /// Type of the chord that has `interval` info.
  public var type: ChordType
  /// Root key of the chord that will built onto.
  public var key: NoteType

  /// Initilizes the chord with type and key.
