Euterpea Exception: No MIDI output device found

Question

I am trying to get started using Haskell's Euterpea library. My first goal was to get it to play a given sound file (e.g. mp3 or wav), but first I ran into an issue following instructions to get it to just play a simple note sound in ghci.

Following the "Setting up MIDI" instructions at Euterpea's web page, I ran

import Euterpea
play $ c 4 qn

in ghci. The 'play' command resulted in the following error message:

Prelude Euterpea> play $ c 4 qn
*** Exception: No MIDI output device found
CallStack (from HasCallStack):
  error, called at ./Euterpea/IO/MIDI/MidiIO.lhs:122:18 in Euterpea-2.0.2-Iz37iWlkpjn2emP4FnvOI1:Euterpea.IO.MIDI.MidiIO

I thought I needed to specify midi output to my machine (macOS Sierra) and found an application called 'Audio MIDI Setup', but it showed that a midi output (my internal speakers) was already specified.

Anyone know what this issue is or how to fix it?

Answer 1

Perhaps you solved this, but for posterity some ideas:

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Sounds like you didn't install and run a MIDI synth (e.g. SimpleSynth) first. AFAICT, Audio MIDI Setup doesn't actually include a software synthesizer, it's more for advanced / hardware MIDI setup.

This should create the MIDI output devices that Euterpea couldn't find there. You may also need to play around with channels (e.g. use playDev n instead of play and work out a value for n from your device list... or even just try 1 through 8)

Either way there's some good Mac-focussed help on Donya's working with MIDI on Mac OS X page. Hope that helps.