Somali ATR or front/back harmony

Saeed 1993 says (p.19):
  Here is the IPA chart given in Saeed 1993 to show the qualities of the two variants of each vowel. I've added a line connecting each pair. Saeed attributes the difference to the Advanced Tongue Root (ATR) feature, but the cited vowel qualities are not consistent with the West African style of ATR differentiation, which is mainly a difference in the first formant, generally associated with vowel height, while Saed's chart makes it seem that the Somali difference is mainly in F2.

The other case that Somali might be compared to is the effects on vowels of so-called emphatic consonants in Arabic.It seems prudent to reserve judgment on the feature(s) involved until some instrumental measurements have been made, but I will provisionally use the terms front and back instead of +ATR and -ATR.

In order to avoid having to deal with browser font issues, I'll use generally capital letters for the back variants from here forward.

The Somali front-back pairs participate in a system of vowel harmony at the level of the phonological word or perhaps some larger phrasal category. Saed p. 32:

As the involvement of adjacent functional categories makes clear, Somali vowel harmony is a phrasal (or 'post-lexical') phenomenon. As is often the case with such phenomena, it is also apparently variable, both across dialects and speakers and across occasions for the same speaker. Saed p. 34:
  Here are the examples given by Saeed. First some near-minimal pairs:
-ATR Gloss +ATR Gloss
dhIs build dibi ox
dIId faint diid refuse
(waan) dIIdAy I fainted (waan) diiday I refused
dhEx center dheg ear
hEEs song gees horn
kEEn bring it! geed tree
dhAr clothes cab drink
rAAc accompany raag be late
nAAs breast daas shop
tOl sew fog far
rOOb rain joog wait
dhUl land gub burn
dUUl fly duul attack
Then some examples of harmony in inflection and with adjacent clitics and function-words:
[bIl] bíl 'month' [bIlO] bilo 'months'
[nirig] niríg 'young female camel' [nirgo] nirgo 'young female camels'
[dhEx] dhéx 'center' [dhExO] dhexo 'centers'
[dheg] dhég 'ear' [dhego] dhego 'ears'
[qOdEEn] qodeen '(they) dug'
[rogeen] rogeen '(they) turned over'
[dAdkA] dádka 'the people' [geedka] gèedka 'the tree'
[hOrtA] hórta 'the front' [gobta] góbta 'the noble person'
[wAAn dIrAy] wàan diray 'I sent it'
[waan diidey] wàan diidey 'I refused it'
[shOw dhIsEE] shòw dhisee 'I may build it'
[show sugee] shòw sugee 'I may wait for it'
[wAAn dIrI dOOnAA] waan díri doonaa 'I will send it'
[waan heli doonaa] waan héli doonaa 'I will find it'
Warner (in Warner, John: Somali Grammar.Mennonite Board in East Africa, Nairobi, 1988) indicates no distinction for /i/, /ii/, /e/, /a/, /ay/, /aw/. For the other vowels he gives:

/ee/  [front] geed 'tree'  gees 'horn' geel 'camels'
      [back]  keen 'bring (it)'        hees  'song'      leef  'to lick'

/aa/  [front] taag 'a high place/ to put high'   aad 'very much'  daan 'jawbone'
      [back]  taag 'strength'   gaal 'unbeliever'    daaq 'to graze'

/o/   [front] fog 'far'  tog 'seasonal river valley'   hog 'hole'
      [back]  lo' 'cattle'  qod 'to dig'  boqol 'hundred'

/oo/  [front] jooj 'to remain'  bood 'to jump'  xoog 'strength'
      [back] roob 'rain' mood 'useful property' doob 'youth'

/u/   [front] dul 'nostril'  sug 'to wait'  duf 'fringe fibers'
      [back]  tuf 'to spit'  dul 'top side' tus 'to show (it)'

/uu/  [front] tuug 'thief' duug 'something old' guur 'shift'
      [back] tuug 'to beg' duul 'fly' suun 'belt'