I have notice from recordings of Paali chanting that Shinhalese people
(in particular) pronounce the vowel 'a' differently for different
words, although the Paali textbooks do not indicate that there are two
pronunciations for the vowel 'a'.
Allow me to illustrate with the phrase "Namo tassa bhagavato arahato
sammaasa.mbuddhassa". I have heard for many times, the second 'a' in
'tassa' and 'buddhassa' pronounced as 'er' instead of 'ah'.