diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -79,4 +79,9 @@
 
 ## 0.8.1.0 -- 2020-03-12
 
-* Eigth version revised B. Changed the sofisticated mechanism to provide real obertones in the 'oberSoXSynth2FDN' function.
+* Eigth version revised B. Changed the sophisticated mechanism to provide real obertones in the 'oberSoXSynth2FDN' function.
+
+## 0.8.2.0 -- 2020-03-12
+
+* Eigth version revised C. Changed the sophisticated mechanism to provide real obertones in the 'oberSoXSynth2FDN' function. Fixed issues with some zeroes
+in the functions. Some code improvements that give more stability. Documentation improvement.
diff --git a/DobutokO/Sound.hs b/DobutokO/Sound.hs
--- a/DobutokO/Sound.hs
+++ b/DobutokO/Sound.hs
@@ -68,7 +68,7 @@
 import Numeric
 import Control.Exception (onException)
 import System.Environment (getArgs)
-import Data.List (isPrefixOf,sort,sortBy)
+import Data.List (isPrefixOf,sort,sortBy,nubBy)
 import Data.Maybe (isJust,isNothing,fromJust)
 import Data.Char (isDigit)
 import qualified Data.Vector as V
@@ -234,7 +234,7 @@
 -- whether there is no \"x.wav\", \"test*\", \"result*\" and \"end.wav\" files in the current directory, because they can be overwritten.
 oberSoXSynth :: Double -> IO ()
 oberSoXSynth x = do
-  let note0 = closestNote x
+  let note0 = if x /= 0.0 then closestNote (abs x) else V.unsafeIndex notes 0
       note1 = pureQuintNote note0
       v0    = oberTones note0
       v1    = oberTones note1
@@ -307,21 +307,24 @@
     _ <- readProcessWithExitCode (fromJust (showE "sox")) (["--combine", "mix"] ++ paths ++ ["result.wav","vol","0.3"]) ""
     mapM_ removeFile paths
 
--- | Similar to 'oberSoXSynth2DN' but instead of 'oberTones' function, it uses volatile function @f::Double -> V.Vector (Double, Double)@ with
--- somewhat sofisticated mechanism to normalize the resulting 'V.Vector' elements @(Double, Double)@. The last one is experimental feature, so
+-- | Similar to 'oberSoXSynth2DN' but instead of 'oberTones' function, it uses volatile function @f::Double -> Vector (Double, Double)@ with
+-- somewhat sophisticated mechanism to normalize the resulting 'V.Vector' elements @(Double, Double)@. The last one is experimental feature, so
 -- it is your responsibility to provide a function so that it does not lead to clipping. In such a case, the result of application of the
 -- 'convertToProperUkrainian' to the 'String' parameter must not be 'V.empty'.
+--
+-- Be aware that the result can be rather unpredictable (the program can even obtain segmentation fault) for not very suitable function.
+-- But for a lot of functions this works well.
 oberSoXSynth2FDN :: (Double -> V.Vector (Double, Double)) -> Double -> Double -> String -> IO ()
 oberSoXSynth2FDN f x y zs
  | V.null . convertToProperUkrainian $ zs = oberSoXSynth x
  | otherwise = do
-    let note0 = closestNote x
+    let note0 = closestNote (if x /= 0.0 then abs x else V.unsafeIndex notes 0)
         note1 = dNote (V.unsafeIndex (intervalsFromString zs) 0) note0
-        g0    = V.fromList . sortBy (\(x1,_) (x2,_) -> compare x1 x2) . V.toList . V.map (\(noteX, amplX) -> (closestNote noteX, abs (amplX - (fromIntegral .
-           truncate $ amplX)))) . f
-        g k   = if V.null (g0 k) then V.empty
-                else V.takeWhile (\w -> compare (fst w) (V.unsafeIndex notes 107) /= GT && compare (snd w) 0.001 == GT) . V.imap (\i (noteY,z0) ->
-                  (fromIntegral (i + 1) * (fst . V.unsafeIndex (g0 k) $ 0), z0)) . g0 $ k
+        g0    = V.fromList . nubBy (\(x1,_) (x2,_) -> x1 == x2) . sortBy (\(x1,_) (x2,_) -> compare x1 x2) . V.toList . V.map (\(noteX, amplX) ->
+           if noteX <= 0.0 then (fromIntegral 2 * note0, abs (amplX - (fromIntegral . truncate $ amplX))) else (closestNote noteX,
+             abs (amplX - (fromIntegral . truncate $ amplX)))) . f
+        g k   = V.takeWhile (\w -> compare (fst w) (V.unsafeIndex notes 107) /= GT && compare (snd w) 0.001 == GT) .
+                   V.imap (\i (noteY,z0) -> (fromIntegral (i + 1) * (fst . V.unsafeIndex (g0 k) $ 0), z0)) . g0 $ k 
         v0    = g note0
         v1    = if isNothing note1 then V.empty
                 else g . fromJust $ note1
@@ -333,7 +336,8 @@
             "vol", showFFloat (Just 4) amplN $ show 0] "") vec
     _ <- readProcessWithExitCode (fromJust (showE "sox")) ["-r22050", "-n", "testA.wav", "synth", showFFloat (Just 4) y $ show 0,"sine",
        showFFloat (Just 4) note0 $ show 0] ""
-    if isNothing note1 then do oberSoXSynthHelp v0
+    if isNothing note1 then do
+      oberSoXSynthHelp v0
     else do 
       _ <- readProcessWithExitCode (fromJust (showE "sox")) ["-r22050", "-n", "testB.wav", "synth", showFFloat (Just 4) y $ show 0,"sine",
          showFFloat (Just 4) (fromJust note1) $ show 0] ""
@@ -342,7 +346,8 @@
     paths0 <- listDirectory "."
     let paths = sort . filter (isPrefixOf "test") $ paths0
     _ <- readProcessWithExitCode (fromJust (showE "sox")) (["--combine", "mix"] ++ paths ++ ["result.wav","vol","0.3"]) ""
-    mapM_ removeFile paths      
+    mapM_ removeFile paths
+   
 
 -- | For the given frequency it generates a musical sound with a timbre. The main component of the sound includes the lower pure quint,
 -- which can be in the same octave or in the one with the number lower by one. Please, check before executing
diff --git a/dobutokO2.cabal b/dobutokO2.cabal
--- a/dobutokO2.cabal
+++ b/dobutokO2.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                dobutokO2
-version:             0.8.1.0
+version:             0.8.2.0
 synopsis:            A program and a library to create experimental music from a mono audio and a Ukrainian text
 description:         It can also create a timbre for the notes
 homepage:            https://hackage.haskell.org/package/dobutokO2