Most tautonymic words, as well as consisting of a repeated letter/group of letters, are also phonetically tautonymic, the 2 identical letter groups having identical pronunciations. On the other hand, there exist tautonymic words with a difference in pronunciation between the 2 identical letter groups. The degree of audible difference varies. it may be obvious as in ISIS, a river in Oxford, and in the TSETSE fly; or the difference may be more subtle.
"Tautonymic Sights and Sounds,"
Word Ways: Vol. 44
, Article 18.
Available at: https://digitalcommons.butler.edu/wordways/vol44/iss3/18