gistfile1.txt

import qualified Sound.JACK.MIDI as MIDI
import Sound.JACK (NFrames(NFrames), )

import qualified Sound.MIDI.Message as Msg
import qualified Sound.MIDI.Message.Channel as Ch
import Data.IORef

mutableValue :: IO (IORef Int)
mutableValue = newIORef (0 :: Int)

startMidiListener :: IO ()
startMidiListener = MIDI.main (makeMidiEventHandler counter)

makeMidiEventHandler :: IORef Int -> NFrames -> (NFrames, Msg.T) -> IO (NFrames, Msg.T)
makeMidiEventHandler counter (NFrames cycleStart) (tf@(NFrames t), e) = do
    putStrLn message
    modifyIORef counter (+ 1)
    incr <- readIORef counter
    putStrLn (show incr)
    return (tf, e)