diff --git a/csound-expression-typed.cabal b/csound-expression-typed.cabal
--- a/csound-expression-typed.cabal
+++ b/csound-expression-typed.cabal
@@ -1,5 +1,5 @@
 Name:          csound-expression-typed
-Version:       0.0.5.1
+Version:       0.0.5.2
 Cabal-Version: >= 1.6
 License:       BSD3
 License-file:  LICENSE
diff --git a/src/Csound/Typed/Control.hs b/src/Csound/Typed/Control.hs
--- a/src/Csound/Typed/Control.hs
+++ b/src/Csound/Typed/Control.hs
@@ -45,7 +45,9 @@
         proxy :: SE a -> a
         proxy = const undefined
 
--- | Sets total duration to the given value.
+-- | Sets the global duration of the file or output signal to the given value.
+-- It should be used only once! The proper place is in the top-most
+-- expression before sending to @dac@ or @writeWav@.
 setDur :: Sigs a => D -> a -> a
 setDur mdt as = toTuple $ do
     dt <- toGE mdt