diff --git a/csound-expression-opcodes.cabal b/csound-expression-opcodes.cabal
--- a/csound-expression-opcodes.cabal
+++ b/csound-expression-opcodes.cabal
@@ -1,5 +1,5 @@
 Name:          csound-expression-opcodes
-Version:       0.0.3
+Version:       0.0.3.1
 Cabal-Version: >= 1.6
 License:       BSD3
 License-file:  LICENSE
diff --git a/src/Csound/Typed/Opcode/RealtimeMIDI.hs b/src/Csound/Typed/Opcode/RealtimeMIDI.hs
--- a/src/Csound/Typed/Opcode/RealtimeMIDI.hs
+++ b/src/Csound/Typed/Opcode/RealtimeMIDI.hs
@@ -408,8 +408,8 @@
 -- > kamplitude  ampmidid  kvelocity, idecibels
 --
 -- csound doc: <http://www.csounds.com/manual/html/ampmidid.html>
-ampmidid ::  Msg -> D -> D -> Sig
-ampmidid _ b1 b2 = Sig $ f <$> unD b1 <*> unD b2
+ampmidid ::  D -> D -> Sig
+ampmidid b1 b2 = Sig $ f <$> unD b1 <*> unD b2
     where f a1 a2 = opcs "ampmidid" [(Ir,[Ir,Ir]),(Kr,[Kr,Ir])] [a1,a2]
 
 -- |