Orpheus was inspired by Dion, an AST/Semantic Programming Environment created by Ryan Fleury (developer of The Melodist) and Allen Webster (developer of 4coder). Orpheus takes this approach of Semantic Programming (programming within the programming concepts rather than a textual or visual language) and applies it to natural (and constructed) languages.
The idea is to store generic grammatical concepts and semantic information. The user directly inputs these concepts into the editor, and the editor will automatically determine the correct forms and structure within the target language. The editor also allows linking between different parts of the underlying information, which allows for things like anaphora (e.g. pronouns) whose form can be automatically determined by the editor. Changing something will also change it's links. In the case of anaphora, changing the referenced phrase will also automatically change the anaphora's form.