diff --git a/sample-frame.cabal b/sample-frame.cabal
--- a/sample-frame.cabal
+++ b/sample-frame.cabal
@@ -1,11 +1,10 @@
 Name:             sample-frame
-Version:          0.0.2
+Version:          0.0.3
 License:          BSD3
 License-File:     LICENSE
 Author:           Henning Thielemann <haskell@henning-thielemann.de>
 Maintainer:       Henning Thielemann <haskell@henning-thielemann.de>
 Homepage:         http://www.haskell.org/haskellwiki/Synthesizer
-Package-URL:      http://code.haskell.org/~thielema/sample-frame/core/
 Category:         Sound
 Synopsis:         Handling of samples in an (audio) signal
 Description:
@@ -21,9 +20,18 @@
    Maybe we add 5+1 channels or so in future.
    .
    This is used by packages @sox@, @alsa@, @synthesizer@.
-Tested-With:       GHC==6.10.4
-Cabal-Version:     >=1.2
+Tested-With:       GHC==7.4.2
+Cabal-Version:     >=1.6
 Build-Type:        Simple
+
+Source-Repository this
+  Tag:         0.0.3
+  Type:        darcs
+  Location:    http://code.haskell.org/~thielema/sample-frame/core/
+
+Source-Repository head
+  Type:        darcs
+  Location:    http://code.haskell.org/~thielema/sample-frame/core/
 
 Flag buildBenchmarks
   description: Build benchmark executables
diff --git a/src/Sound/Frame/Stereo.hs b/src/Sound/Frame/Stereo.hs
--- a/src/Sound/Frame/Stereo.hs
+++ b/src/Sound/Frame/Stereo.hs
@@ -1,7 +1,11 @@
 {-
 This data type can be used as sample type for stereo signals.
 -}
-module Sound.Frame.Stereo (T, left, right, cons, map, ) where
+module Sound.Frame.Stereo (
+   T, left, right, cons, map,
+   Channel(..), select,
+   interleave, sequence, liftApplicative,
+   ) where
 
 import qualified Sound.Frame as Frame
 
@@ -16,7 +20,7 @@
 
 import Test.QuickCheck (Arbitrary(arbitrary), )
 
-import Prelude hiding (map, )
+import Prelude hiding (Either(Left, Right), map, sequence, )
 
 
 data T a = Cons {left, right :: !a}
@@ -40,6 +44,32 @@
 {-# INLINE map #-}
 map :: (a -> b) -> T a -> T b
 map f (Cons l r) = Cons (f l) (f r)
+
+
+data Channel = Left | Right
+
+{-# INLINE select #-}
+select :: T a -> Channel -> a
+select x c =
+   case c of
+      Left -> left x
+      Right -> right x
+
+{-# INLINE interleave #-}
+interleave :: (T a, T b) -> T (a,b)
+interleave = uncurry (liftA2 (,))
+
+{-# INLINE sequence #-}
+sequence :: (Functor f) => f (T a) -> T (f a)
+sequence x = cons (fmap left x) (fmap right x)
+
+{-# INLINE liftApplicative #-}
+liftApplicative ::
+   (Applicative f) =>
+   (f a -> f b) -> f (T a) -> f (T b)
+liftApplicative proc =
+   Trav.sequenceA . fmap proc . sequence
+
 
 instance Functor T where
    {-# INLINE fmap #-}
diff --git a/src/SpeedTest.hs b/src/SpeedTest.hs
--- a/src/SpeedTest.hs
+++ b/src/SpeedTest.hs
@@ -37,6 +37,14 @@
 real    0m3.017s
 user    0m2.844s
 sys     0m0.168s
+
+
+GHC-7.2.1:
+
+Storable.Traversable instance:
+real    0m3.794s
+user    0m3.564s
+sys     0m0.196s
 -}
 stereo :: SV.Vector (Stereo.T Int16)
 stereo =
@@ -76,6 +84,13 @@
 real    0m47.021s
 user    0m46.827s
 sys     0m0.108s
+
+GHC-7.2.1:
+
+Storable.Traversable instance:
+real    0m3.933s
+user    0m3.864s
+sys     0m0.068s
 -}
 stereoSum :: SV.Vector (Stereo.T Int16) -> Stereo.T Int16
 stereoSum =