Spooky Smoothing in Backstreet's Back

In honor of the spookiest month of the year, I've been watching the Halloween-themed video "Everybody (Backstreet's Back)" by the famous 90s band the Backstreet Boys.

Despite having listened to it for several years, this week was the first time I noticed that the chorus was not, in fact, "everybody (yeah) rock your body (yeah)", but in fact had a phantom 'yeah' added in: "Everybody yeah (yeah) rock your body yeah (yeah)." I checked several lyrics sites to confirm this and yes, these are the official lyrics. How did I miss this yeah for so long?

Well, the introduction of the song has a very clear extra yeah.

Everybody, yeah. Rock your body, yeah.
ɛvrɪbadɪ jɛə. rɑk jo bɑdɪ jɛə

You can clearly hear that there is a 'y' in that 'yeah'. Compare how they say "body yeah" with the next section, with no 'yeah':

Rock your body right.
rɑk jo bɑdɪ rait

It turns out that this pattern of a lyrics plus a 'yeah' actually repeats in every chorus. But I had never noticed because, well, there is some pretty wild smoothing going on:

Everybodye (yeah) rock your bodye (yeah)
ɛvrɪbadɪɛ (jɛə) rɑk jo bɑdɪɛ (jɛə)

Did you catch it? [ɛvrɪbadɪ jɛə] has become [ɛvrɪbadɪɛ] or [ɛvrɪbadɪə]. The [j] has mysteriously disappeared!

It doesn't help that the Backstreet Boys use a lax-HAPPY vowel in 'everybody' and 'body,' which means there is less distance between the 'ih' in 'everybody' and the 'eh' of the swallowed yeah. I think I would have noticed it if they had used a tense HAPPY-vowel - it would have been harder to ignore the difference in vowel quality.

This particular conversion of a falling diphthong to a monophtong is called smoothing, or at least it is in the study of English. Indeed, the only other example I can think of smoothing happens in RP, where a word like 'fire' /faɪə/ can become [faə].

Is this part of some larger linguistic trend? Not that I can tell. The lax-HAPPY is definitely very typical of the period (as I shall write about soon), but I don't think smoothing of this sort was widespread. This smoothing seems to have been motivated by the meldody, which was melismatic in the first chorus ("Everybody, ye-e-ah") and then became syllabic in the following choruses ("everybody-e"). It was easier to reduce the 'yeah' to a monophthong than to try and produce the full form, especially since the full form was repeated by the backing vocals anyway.