The correct spelling for the phrase "art up and up" is /ɑːt ʌp ənd ʌp/. The sound represented by the letter "a" is pronounced as the "ar" sound, as in "car" or "bar". The "t" sound is followed by a glottal stop, which is represented by the apostrophe symbol. The next "u" sound is a schwa, similar to the "uh" sound in "butter". Finally, the second "up" is spelled as it sounds. This phrase means something that is continually improving and getting better.