diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -63,7 +63,7 @@
 
 # exclude installed versions of Haskore, because we want to use the local one
 HUGS_PACKAGE_PATH = \
-   {Hugs}/libraries:{Hugs}/packages/*:$(subst $(space),$(colon),$(patsubst %,/usr/local/lib/hugs/packages/%,event-list midi markov-chain non-negative special-functors data-accessor transformers explicit-exception binary utility-ht))
+   {Hugs}/libraries:{Hugs}/packages/*:$(subst $(space),$(colon),$(patsubst %,/usr/local/lib/hugs/packages/%,event-list midi markov-chain non-negative special-functors data-accessor transformers monoid-transformer explicit-exception binary utility-ht))
 #   $(subst $(space),$(colon),$(patsubst %,{Hugs}/packages/%,event-list midi markov-chain non-negative record-access))
 
 
diff --git a/haskore.cabal b/haskore.cabal
--- a/haskore.cabal
+++ b/haskore.cabal
@@ -1,5 +1,5 @@
 Name:           haskore
-Version:        0.1
+Version:        0.1.0.1
 License:        GPL
 License-File:   LICENSE
 Author:         Paul Hudak <paul.hudak@yale.edu>, Henning Thielemann
@@ -11,7 +11,7 @@
 Description:
   Compose music using programming features.
   Output in MIDI, CSound, SuperCollider or as an audio signal.
-Tested-With:       GHC==6.4.1, GHC==6.8.2, Hugs==2006.9
+Tested-With:       GHC==6.4.1, GHC==6.8.2, GHC==6.10.4, Hugs==2006.9
 Cabal-Version:     >=1.6
 Build-Type:        Simple
 
@@ -26,12 +26,12 @@
 
 Source-Repository head
   type:     darcs
-  location: http://darcs.haskell.org/haskore/
+  location: http://code.haskell.org/haskore/revised/core
 
 Source-Repository this
   type:     darcs
-  location: http://darcs.haskell.org/haskore/
-  tag:      0.1
+  location: http://code.haskell.org/haskore/revised/core
+  tag:      0.1.0.1
 
 Flag splitBase
   description: Choose the new smaller, split-up base package.
@@ -55,7 +55,7 @@
 
   If flag(splitBase)
     Build-Depends:
-      base >=3,
+      base >=3 && <6,
       array >=0.1 && <1.0,
       containers >=0.1 && <1.0,
       random >=1.0 && <2.0,
@@ -153,6 +153,7 @@
     Haskore.General.LoopTreeTaggedGen,
     Haskore.General.GraphRecursiveGen,
     Haskore.General.GraphTaggedGen,
+    Haskore.General.LetRec,
     Haskore.General.Map,
     Haskore.General.TagDictionary,
     Haskore.General.Utility
diff --git a/src/Haskore/General/LetRec.hs b/src/Haskore/General/LetRec.hs
new file mode 100644
--- /dev/null
+++ b/src/Haskore/General/LetRec.hs
@@ -0,0 +1,67 @@
+module Haskore.General.LetRec where
+
+import Data.Tuple.HT (mapFst, mapSnd, )
+import qualified Data.Map as Map
+
+
+data Expr =
+    Const String
+  | Append Expr Expr
+  | Var Var
+   deriving (Show)
+
+type Var = Int
+type Count = Int
+
+
+knot ::
+   (Count, ([Expr], (Expr, a)) -> ([Expr], (Expr, b))) ->
+   (Count, ([Expr], a) -> ([Expr], b))
+knot (count, f) =
+   (succ count,
+    \(equs0, a) ->
+       let (equs1, (rhs, b)) = f (equs0, (Var count, a))
+       in  (rhs : equs1, b))
+
+beginKnot ::
+   (a -> b) ->
+   (Count, ([Expr], a) -> ([Expr], b))
+beginKnot f =
+   (0, mapSnd f)
+
+endKnot ::
+   (Count, ([Expr], a) -> ([Expr], b)) ->
+   (a -> ([Expr], b))
+endKnot f a = snd f ([], a)
+
+
+exampleLet ::
+   (Expr, (Expr, ())) ->
+   (Expr, (Expr, Expr))
+exampleLet (a,(b,())) =
+   (Append (Const "ab") b,
+    (Append (Const "c") a,
+     a))
+
+{-
+Maybe we can replace manual repeated application of 'knot'
+by a type class method.
+-}
+exampleEqus :: ([Expr], Expr)
+exampleEqus =
+   mapFst reverse $
+   endKnot (knot (knot (beginKnot exampleLet))) ()
+
+exampleResult :: String
+exampleResult =
+   let mapExpr = Map.fromAscList $ zip [0..] $ fst exampleEqus
+       resolve x =
+          case x of
+             Const str -> str
+             Append a b ->
+                resolve a ++ resolve b
+             Var n -> Map.findWithDefault
+                (error $ "unknown variable id " ++ show n ++ " - bug in 'knot'?")
+                n mapRes
+       mapRes = fmap resolve mapExpr
+   in  resolve $ snd exampleEqus
diff --git a/src/Haskore/Interface/MIDI/Write.lhs b/src/Haskore/Interface/MIDI/Write.lhs
--- a/src/Haskore/Interface/MIDI/Write.lhs
+++ b/src/Haskore/Interface/MIDI/Write.lhs
@@ -405,11 +405,11 @@
 \end{haskelllisting}
 
 
-*****
+% ***
 The MIDI volume handling is still missing.
 One cannot express the Volume in terms of the velocity!
 Thus we need some new event constructor for changed controller values.
-*****
+% ***
 
 \begin{haskelllisting}