O

This letter can represent one of five sounds:


1. This letter is typically /ɑ/ whenever two consonants follow it:

E.g.
lock, dock, flock, stock
concoction -> concoccion
to concoct -> ta concocte
not
knot -> nott


2. This letter is /oʊ/ when an -e follows a single consonant:

E.g.
cove, stove, lone, code
to explode
to corrode -> ta corrode
to condone -> ta condone
to suppose -> ta sopose
to postpone -> ta postpone
to oppose -> to opose
throne -> þrone

Also before -ld:
bold, cold, fold, gold, hold, mold, old

It is also /oʊ/ when at the end of words:
tomorrow -> tomòro
tarot -> târo
sparrow -> spâro
window -> ɯindo

In single syllable words, a -ɯ will follow:
show -> shoɯ
blow -> bloɯ
flow -> floɯ

Where verbs are stressed on their first syllable, the o is followed by -e:
E.g.
to lasso -> ta lassoe
to follow -> ta fóloe

-ɯ shows back up in gerunds:
lassoɯiŋ
fóloɯiŋ


3. This letter is /ɔ/ when -h follows it. 
This is typically used in irregular past tenses and the nouns derived therefrom:

E.g.
bought -> boht
caught -> coht
fought -> foht
sought -> soht
thought -> þoht


4. This letter is /ə/ in many cases where it's not stressed:

E.g.
monotheism -> monoþýism /ˌmɑnəˈθiˌɪzəm/
museum -> m̃usíom /mjuˈziəm/
stadium -> stâdiom /ˈsteɪdiəm/
to condone -> ta condone /tə kənˈdoʊn/
to suppose -> ta sopose /tə səˈpoʊz/
*run -> ron /rən/
*Monday /ˈmənˌdeɪ/

*u cannot come between m, n, r; o replaces u in these instances.


5. This letter can also be /ər/ when followed by an -r and isn't stressed:

E.g.
administrator -> admìnistraitor /ədˈmɪnəˌstreɪɾər/
gopher -> gofor /ˈɡoʊfər/
educator -> eᶁucaitor /ˈɛdʒəˌkeɪɾər/
hammer -> hamor /ˈhæmər/