         public var scaleType: ScaleType
         public var pitch: Float
         public var transpositionTone: Tone
-        public var octaveRange: CountableRange<Int>
+        public var octaveRange: OctaveRange
     }
 
     /// Generate frequencies for each tones.

    static func tunePure(
        pitch: Float,
        transpositionTone: Tone,
        octaveRange: CountableRange<Int>,
        pureType: ScaleType.Pure,
        rootTone: Tone
    ) -> [Harmony] {

    static func tuneEqual(
        pitch: Float,
        transpositionTone: Tone,
        octaveRange: OctaveRange
    ) -> [Harmony] {
        let tuningBase = equalBase(pitch: pitch, transpositionTone: transpositionTone)
        var harmonies = [Harmony]()
