diff --git a/music-parts.cabal b/music-parts.cabal
--- a/music-parts.cabal
+++ b/music-parts.cabal
@@ -1,6 +1,6 @@
 
 name:               music-parts
-version:            1.2
+version:            1.3
 cabal-version:      >= 1.2
 author:             Hans Hoglund
 maintainer:         Hans Hoglund
@@ -14,7 +14,7 @@
 description: 
     Abstract representation of musical parts and instruments.
 
-    This library is part of the Haskell Music Suite, see <http://musicsuite.github.com>.
+    This library is part of the Music Suite, see <http://musicsuite.github.com>.
 
 library                    
     build-depends: 
diff --git a/src/Music/Parts.hs b/src/Music/Parts.hs
--- a/src/Music/Parts.hs
+++ b/src/Music/Parts.hs
@@ -1,2 +1,72 @@
 
 module Music.Parts where
+    
+{-
+    ## Terminology: Voice vs Part
+    
+    A voice is a container of notes (non-overlapping)
+    
+    A part is an identifier for a set of singers/musicians AND all the notes in a score
+    designated for this set of performers. Part extraction has the type
+    
+        extractParts :: HasPart a => Score a -> [Score a]
+    
+    I.e. in a score for piano and ensemble, certain notes may be *in the piano part*, i.e.
+    designated for the piano. Typically, a part is monophonic or polyphonic. A monophonic
+    part is a voice, i.e.
+
+        -- | Are there overlapping notes?
+        isMonophonic :: Score a -> Bool
+
+        -- | Fails for polyphonic scores.
+        scoreToVoice :: Score a -> Voice (Maybe a)
+    
+    A polyphonic part contains several voices, i.e.
+
+        scoreToVoices :: Score a -> [Voice (Maybe a)]  
+
+
+    A part is any type a that satisfies (Ord a, Show a).
+    Optionally, we may add a contraint (HasPartName a), i.e.
+
+        class HasPartName a where
+            partName :: a -> String
+            partAbbr :: a -> String
+    
+    
+    These contraints are used when printing scores (to get the order of the parts and their name).
+
+        Vln1, Vln2 etc.
+
+    Often we want to group parts, i.e.
+
+        Chorus {
+            Sop  { Sop1 Sop2 }
+            Alto { Alto1 Alto2 }
+            Ten  { Ten1 Ten 2 }
+            Bass { Bass1 Bass2 }
+        }
+        Orchestra {
+            Woodwinds { ... }
+            Brass { ... }
+            Perc { ... }
+            Strings { ... }
+        }
+
+
+    isInGroup :: Group -> Part -> Bool
+    partGroups :: Part -> [Group]
+
+
+    partGroup :: (Part -> [Group] -> a) -> Group -> a
+    tree :: (a -> [Tree a] -> b) -> Tree a -> b
+    
+    
+    data MyPart
+        = Fl
+        | Sop
+        | Vl1
+        | Vl2
+        | Pno
+
+-}