diff --git a/Control/Artery.hs b/Control/Artery.hs
--- a/Control/Artery.hs
+++ b/Control/Artery.hs
@@ -10,6 +10,7 @@
     , feedback
     , delay1
     , delay
+    , cartridge
     , module Control.Arrow) where
 
 import qualified Control.Category
@@ -19,6 +20,8 @@
 import Data.Monoid
 import Data.Profunctor
 import Control.Monad.Trans.State
+import Control.Concurrent
+import Control.Monad.IO.Class
 
 -- | 'Artery' is a device that produces a value from the input every beat.
 newtype Artery m i o = Artery { unArtery :: forall r. i -> (o -> Artery m i o -> m r) -> m r }
@@ -88,6 +91,12 @@
     fromInteger = pure . fromInteger
     {-# INLINE fromInteger #-}
 
+instance Fractional o => Fractional (Artery m i o) where
+    (/) = liftA2 (/)
+    {-# INLINE (/) #-}
+    recip = fmap recip
+    fromRational = pure . fromRational
+
 instance Monoid o => Monoid (Artery m i o) where
     mempty = pure mempty
     {-# INLINE mempty #-}
@@ -148,11 +157,7 @@
 runList ar (x:xs) = unArtery ar x $ \y cont -> (y:) <$> runList cont xs
 runList _ [] = pure []
 
-triggered :: Monoid a => [a] -> Artery m Bool a
-triggered w = go [] where
-    zipLong (x:xs) (y:ys) = mappend x y : zipLong xs ys
-    zipLong xs [] = xs
-    zipLong [] ys = ys
-    go wav = Artery $ \i cont -> case (if i then id else zipLong w) wav of
-        x:xs -> cont x (go xs)
-        _ -> cont mempty (go [])
+cartridge :: MonadIO m => MVar (Artery m i o) -> Artery m i o
+cartridge ref = go where
+    go = Artery $ \i cont -> liftIO (takeMVar ref)
+        >>= \a -> unArtery a i $ \o a' -> liftIO (putMVar ref a') >> cont o go
diff --git a/artery.cabal b/artery.cabal
--- a/artery.cabal
+++ b/artery.cabal
@@ -1,5 +1,5 @@
 name:                artery
-version:             0.1
+version:             0.1.1
 synopsis:            A simple, arrow-based reactive programming
 description:         This package only provides Artery type and associated operations.
 homepage:            https://github.com/fumieval/artery
@@ -16,6 +16,6 @@
   exposed-modules:     Control.Artery
   -- other-modules:       
   other-extensions:    Rank2Types
-  build-depends:       base == 4.*, containers, profunctors >= 3.0 && < 5, transformers == 0.3.*
+  build-depends:       base == 4.*, containers, profunctors >= 3.0 && < 5, transformers >= 0.3 && <5
   -- hs-source-dirs:      
   default-language:    Haskell2010