         return Chord(intervals: inverted, name: name, inversion: modN)
     }
 
+    public static let Triads : [Chord] = [Chord.MajorTriad,
+    Chord.MinorTriad, Chord.AugmentedTriad, Chord.DiminishedTriad]
     public static let MajorTriad = Chord(intervals: [0, 4, 7],
         name: "Major triad")
     public static let MinorTriad = Chord(intervals: [0, 3, 7],

    public static let DominantSeventhFlatFive = Chord(intervals: [0, 4, 6, 10],
        name: "Dominant seventh flat five")

    public static let MajorNinth = Chord(intervals: [0, 4, 7, 11, 14],
        name: "Major ninth")
    public static let DominantNinth = Chord(intervals: [0, 4, 7, 10, 14],
        name: "Dominant ninth")
    public static let MinorMajorNinth = Chord(intervals: [0, 3, 7, 11, 14],
        name: "Dominant ninth")
    public static let MinorNinth = Chord(intervals: [0, 3, 7, 10, 14],
        name: "Minor ninth")
    public static let AugmentedMajorNinth = Chord(intervals: [0, 4, 8, 11, 14],
        name: "Augmented-major ninth")
    public static let AugmentedNinth = Chord(intervals: [0, 4, 8, 10, 14],
        name: "Augmented ninth")
    public static let HalfDiminishedNinth = Chord(intervals: [0, 3, 6, 10, 14],
        name: "Half-diminished ninth")
    public static let HalfDiminishedMinorNinth = Chord(intervals: [0, 3, 6, 10, 13],
        name: "Half-diminished minor ninth")
    public static let DiminishedNinth = Chord(intervals: [0, 3, 6, 9, 14],
        name: "Diminished ninth")
    public static let DiminishedMinorNinth = Chord(intervals: [0, 3, 6, 9, 13],
        name: "Diminished minor ninth")

}

    public static let DiminishedTriad = Chord(intervals: [0, 3, 6],
        name: "Diminished triad")

    public static let Tetrads : [Chord] = [Chord.DominantSeventh,
        Chord.MajorSeventh, Chord.MinorMajorSeventh, Chord.MinorSeventh,
        Chord.AugmentedMajorSeventh, Chord.AugmentedSeventh,
        Chord.HalfDiminishedSeventh, Chord.DiminishedSeventh,
        Chord.DominantSeventhFlatFive]
    public static let DominantSeventh = Chord(intervals: [0, 4, 7, 10],
        name: "Dominant seventh")
    public static let MajorSeventh = Chord(intervals: [0, 4, 7, 11],
