diff --git a/Sound/Tidal/Parse.hs b/Sound/Tidal/Parse.hs
--- a/Sound/Tidal/Parse.hs
+++ b/Sound/Tidal/Parse.hs
@@ -11,7 +11,7 @@
 import Data.Colour.Names
 import Data.Colour.SRGB
 import GHC.Exts( IsString(..) )
-import Data.Monoid
+-- import Data.Monoid
 -- import qualified Data.Semigroup as Sem
 import Control.Exception as E
 import Control.Applicative ((<$>), (<*>), pure)
@@ -21,9 +21,11 @@
 import Sound.Tidal.Pattern
 import Sound.Tidal.Time (Arc, Time)
 
+{-
 #ifdef TIDAL_SEMIGROUP
 import qualified Data.Semigroup as Sem
 #endif
+-}
 
 -- | AST representation of patterns
 
@@ -44,6 +46,7 @@
             | TPat_pE (TPat Int) (TPat Int) (TPat Integer) (TPat a)
             deriving (Show)
 
+{-
 #ifdef TIDAL_SEMIGROUP
 instance Sem.Semigroup (TPat a) where
   (<>) = TPat_Overlay
@@ -56,6 +59,7 @@
    mempty = TPat_Silence
    mappend = TPat_Overlay
 #endif
+-}
 
 toPat :: Enumerable a => TPat a -> Pattern a
 toPat = \case
@@ -260,7 +264,7 @@
 pPolyIn :: Parseable a => Parser (TPat a) -> Parser (TPat a)
 pPolyIn f = do ps <- brackets (pSequence f `sepBy` symbol ",")
                spaces
-               pMult $ mconcat ps
+               pMult $ foldr TPat_Overlay TPat_Silence ps
 
 pPolyOut :: Parseable a => Parser (TPat a) -> Parser (TPat a)
 pPolyOut f = do ps <- braces (pSequenceN f `sepBy` symbol ",")
@@ -270,11 +274,11 @@
                            i <- integer <?> "integer"
                            return $ Just (fromIntegral i)
                         <|> return Nothing
-                pMult $ mconcat $ scale base ps
+                pMult $ foldr TPat_Overlay TPat_Silence $ scale base ps
              <|>
              do ps <- angles (pSequenceN f `sepBy` symbol ",")
                 spaces
-                pMult $ mconcat $ scale (Just 1) ps
+                pMult $ foldr TPat_Overlay TPat_Silence $ scale (Just 1) ps
   where scale _ [] = []
         scale base (ps@((n,_):_)) = map (\(n',p) -> TPat_Density (TPat_Atom $ fromIntegral (fromMaybe n base)/ fromIntegral n') p) ps
 
diff --git a/Sound/Tidal/Pattern.hs b/Sound/Tidal/Pattern.hs
--- a/Sound/Tidal/Pattern.hs
+++ b/Sound/Tidal/Pattern.hs
@@ -4,7 +4,7 @@
 module Sound.Tidal.Pattern where
 
 import Control.Applicative
-import Data.Monoid
+-- import Data.Monoid
 import Data.Fixed
 import Data.List
 import Data.Maybe
@@ -24,9 +24,11 @@
 import Text.Show.Functions ()
 import qualified Control.Exception as E
 
+{-
 #ifdef TIDAL_SEMIGROUP
 import qualified Data.Semigroup as Sem
 #endif
+-}
 
 -- | The pattern datatype, a function from a time @Arc@ to @Event@
 -- values. For discrete patterns, this returns the events which are
@@ -165,6 +167,7 @@
                  (xs (s',e'))
                 )
 
+{-
 #ifdef TIDAL_SEMIGROUP
 -- | @mappend@ a.k.a. @<>@ is a synonym for @overlay@.
 instance Sem.Semigroup (Pattern a) where
@@ -180,6 +183,7 @@
   mempty = silence
   mappend = overlay
 #endif
+-}
 
 instance Monad Pattern where
   return = pure
diff --git a/Sound/Tidal/Transition.hs b/Sound/Tidal/Transition.hs
--- a/Sound/Tidal/Transition.hs
+++ b/Sound/Tidal/Transition.hs
@@ -39,10 +39,11 @@
 superwash _ _ _ _ _ _ [] = silence
 superwash _ _ _ _ _ _ (p:[]) = p
 superwash fout fin delay durin durout now (p:p':_) =
-   (playWhen (< (now + delay)) p') <>
-   (playWhen (between (now + delay) (now + delay + durin)) $ fout p') <>
-   (playWhen (between (now + delay + durin) (now + delay + durin + durout)) $ fin p) <>
-   (playWhen (>= (now + delay + durin + durout)) $ p)
+   stack [(playWhen (< (now + delay)) p'),
+          (playWhen (between (now + delay) (now + delay + durin)) $ fout p'),
+          (playWhen (between (now + delay + durin) (now + delay + durin + durout)) $ fin p),
+          (playWhen (>= (now + delay + durin + durout)) $ p)
+         ]
  where
    between lo hi x = (x >= lo) && (x < hi)
 
diff --git a/tidal.cabal b/tidal.cabal
--- a/tidal.cabal
+++ b/tidal.cabal
@@ -1,5 +1,5 @@
 name:                tidal
-version:             0.9.8
+version:             0.9.9
 synopsis:            Pattern language for improvised music
 -- description:
 homepage:            http://tidalcycles.org/
@@ -12,7 +12,7 @@
 category:            Sound
 build-type:          Simple
 cabal-version:       >=1.10
-tested-with:         GHC == 7.10.3, GHC == 8.0.1
+tested-with:         GHC == 7.10.3, GHC == 8.0.1, GHC == 8.4.1
 
 Extra-source-files: README.md CHANGELOG.md tidal.el doc/tidal.md