I was trying to a very simple mp3 output using the following command:
$ abcde -n -p -P -o mp3:"--preset voice"
but this was failing saying that "Unix pipes not compatible with multiple outputs". It looks like the code checks the number of outputs using spaces:
NUM_OUTPUT_TYPES="$(echo "$OUTPUTTYPE" | tr , \ | wc -w )"
which is clearly assuming that $OUTPUTTYPE doesn't already have spaces in it.
Trivial fix could be to just `tr --delete \ ` or something to delete real spaces before replacing commas with spaces.