How to annotate the difference between blended vowels and non-blended vowels

Question

Similar to this question about consonants, I'm wondering how you annotate with IPA (or any other system if IPA doesn't support it) the difference between blending vowels together (morphing between multiple vowels) and discretely shifting between them.

For example, the word "wow" is really like 3 different vowel sounds from what it seems. So I would maybe do /ʊɛʊ/. But this is blending the sounds together.

A different way to do it to demonstrate non-blending is to use glottal stops, /ʊʔɛʔʊ/, or "ʊ'ɛ'ʊ". But that is essentially putting a pause between the sounds which is the extreme.

In the middle, in between blending and putting pauses between the sounds, is just shifting from one to the next without blending. A way to replicate this is to pronounce each long, and transition to the next quickly, so "ʊʊʊʊʊʊʊɛɛɛɛɛɛɛɛɛʊʊʊʊʊʊʊʊ". If you do this quickly but not so quickly as to morph or blend them together, then it's not a glottal stop and not a blend, so it's a ________ I don't know, a discrete shift.

Wondering how to annotate this in IPA. It seems then there are 3 types:

• blending
• discretely shifting
• glottal stops

Wondering how to write all 3. If there are more ways to do it than these 3 types, that would be good to know too!

Answer 1

There are a couple of ways that the IPA can annotate such differences. The first is a tiebar: u͡a (unicode 0361) or u͜a (unicode 035C). Use of a tiebar is usually taken to indicate "these two vowels are part of a single phoneme" (i.e., they form a diphthong), which technically indicates something about their behavior in the phonological patterns of the language, but usually also means they are pronounced more "blended" (to use your term).

A way to indicate that the vowels are more "discrete" is to explicitly mark them as members of separate syllables, using a period (as in /a.u/, or if the second syllable is prominent, /aˈu/ or /aˌu/).

A third way one might (ab)use the IPA to denote a "blended" vs "discrete" vowel sequence would be to mark one of the vowels as an onglide or offglide, using /j/ (in place of /i/), /w/ (in place of /u/) or /ɰ/ (in place of /ɯ/). Personally I don't think that's a very good approach, for a couple of related reasons:

1. Technically those symbols represent consonants, not vowels, and so /aj/ ought to be considered a V-C sequence, which makes it no longer just a vowel.
2. In speech the glide-vowel or vowel-glide transition is often quite "blended" and may be indistinguishable from a diphthong solely on auditory or acoustic grounds. In other words, the question of whether English "pie" is transcribed as /pa͜i/ (two phonemes, CV) or /paj/ (three phonemes, CVC) depends more on larger-scale patterns of how the [aɪ] sound(s) behave in different contexts, rather than on how blended or discrete the sounds are (e.g., if English "pie" follows a phonological rule that is followed by other words that are unambiguously CVC and not by words that are unambiguously CV, you might argue on that basis that /paj/ is correct).

As a final aside: when vowels are adjacent in speech with continuous voicing, they will never be fully "discrete". There will always be a period of transition in the vowel quality, because when the jaw/tongue/lips move to make the second vowel gesture, the size and shape of the air mass in the oral cavity changes too, and that change is never instantaneous.