Problem

The Melodyne 4 Trial defaults to the Polyphonic algorithm when loading a new file. Only noticed the artifacts after making a bunch of edits.

Notice how it almost sounds like a chord (i.e. polyphony) at the end of each phrase.

Solution

Don’t use the Polyphonic algorithm for vocal editing. Use Melodic instead.

Note: there is a setting in the menu bar so set the default algorithm, but it doesn’t seem to persist after quitting the application.