[_emacsomancer_]

> The lesson I would draw here is more "minimal pairs aren't sufficient to demonstrate every phoneme" than "it's not a phoneme until a minimal pair exists".

Perhaps. (Minimal pairs are, of course, simply a diagnostic tool.) It would be a pretty unproductive phoneme though.

> I didn't claim and don't believe that English is developing lexical tones. But I do believe that the development of lexical tone in this single unusual word is fundamentally similar to the larger-scale development of tone in other languages, and that the still-obvious relationship between the phrase and the tone sequence makes this a good example to help English speakers understand how it can happen.

I'm not deeply versed in tonogenesis - but that is interesting as a potential source (phrasal tone). I wonder what conditions could lead to phrase-related tonal patterns becoming prominent/frequent enough to be a source of more prototypical lexical tone.

> > And of course there's more than just question-associated tone, there's also focus-associated tonal prosody.

> Very true, but much harder to describe.

It's been discussed fairly extensively though, at least as far back as Jackendoff (1972 or thereabouts).