diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,16 @@
 Changelog
 =========
 
+Version 0.1.2.1
+---------------
+
+*July 27, 2018*
+
+<https://github.com/mstksg/emd/releases/tag/v0.1.2.1>
+
+*   *BUG FIX* Fixed behavior of frequency wrapping to wrap between 0 and 1,
+    instead of 0.5, as claimed!
+
 Version 0.1.2.0
 ---------------
 
@@ -11,6 +21,7 @@
 *   Actually implemented the Hilbert-Huang transform
 *   Allowed for other border handling behaviors during EMD
 *   Changed default stopping conditions for sifting process
+*   Added clamped spline end conditions.
 *   Removed unsized interface
 *   Sifting will now throw runtime exception for singular splining matrices,
     instead of treating the result as a residual.  This might change in the
diff --git a/emd.cabal b/emd.cabal
--- a/emd.cabal
+++ b/emd.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 1b094b03f7c2c369028d76bd580e55e637de3c9d9e63c53dd715fa2bb4187644
+-- hash: eba3e48d66b797a1e9b109e1bb2cc296003754c5adda30419efb80cfee7a1d66
 
 name:           emd
-version:        0.1.2.0
+version:        0.1.2.1
 synopsis:       Empirical Mode Decomposition and Hilbert-Huang Transform
 description:    Please see the README on GitHub at <https://github.com/mstksg/emd#readme>
 category:       Math
diff --git a/src/Numeric/EMD.hs b/src/Numeric/EMD.hs
--- a/src/Numeric/EMD.hs
+++ b/src/Numeric/EMD.hs
@@ -122,6 +122,9 @@
 
 -- | An @'EMD' v n a@ is an Empirical Mode Decomposition of a time series
 -- with @n@ items of type @a@ stored in a vector @v@.
+--
+-- The component-wise sum of 'emdIMFs' and 'emdResidual' should yield
+-- exactly the original series.
 data EMD v n a = EMD { emdIMFs     :: ![SVG.Vector v n a]
                      , emdResidual :: !(SVG.Vector v n a)
                      }
diff --git a/src/Numeric/EMD/Internal/Spline.hs b/src/Numeric/EMD/Internal/Spline.hs
--- a/src/Numeric/EMD/Internal/Spline.hs
+++ b/src/Numeric/EMD/Internal/Spline.hs
@@ -40,9 +40,17 @@
 import qualified Data.Vector.Sized                as SV
 
 -- | End condition for spline
-data SplineEnd a = SENotAKnot
-                 | SENatural
-                 | SEClamped a a
+data SplineEnd a
+    -- | "Not-a-knot" condition: third derivatives are continuous at
+    -- endpoints.  Default for matlab spline.
+    = SENotAKnot
+    -- | \"Natural\" condition: curve becomes a straight line at endpoints.
+    | SENatural
+    -- | \"Clamped\" condition: Slope of curves at endpoints are explicitly
+    -- given.
+    --
+    -- @since 0.1.2.0
+    | SEClamped a a
   deriving (Show, Eq, Ord)
 
 data SplineCoef a = SC { _scAlpha  :: !a      -- ^ a
diff --git a/src/Numeric/HHT.hs b/src/Numeric/HHT.hs
--- a/src/Numeric/HHT.hs
+++ b/src/Numeric/HHT.hs
@@ -162,8 +162,7 @@
     v' = hilbertIm v
     hilbertMag   = SVG.zipWith (\x x' -> magnitude (x :+ x')) v v'
     hilbertPhase = SVG.zipWith (\x x' -> phase (x :+ x')) v v'
-    hilbertFreq  = SVG.map (wrap . (/ (2 * pi))) $ SVG.tail hilbertPhase - SVG.init hilbertPhase
-    wrap         = subtract 0.5 . (`mod'` 1) . (+ 0.5)
+    hilbertFreq  = SVG.map ((`mod'` 1) . (/ (2 * pi))) $ SVG.tail hilbertPhase - SVG.init hilbertPhase
 
 -- | Real part is original series and imaginary part is hilbert transformed
 -- series.  Creates a "helical" form of the original series that rotates