In answer to your question regarding phoneme waveforms in Macintalk,
there are none. The phonemes are generated algorithmically from parameters.
Replacing the phoneme inventory by substituting new parameters (there are
about a dozen for each phoneme) can be done, but the results will not be
satisfactory. This is because phonemes do not exist in isolation. Although
each phoneme in Macintalk is initially described by a few parameters, there
are literally hundreds of phonological rules which are applied to the phoneme
string to modify these parameters given some phonemic context. In addition,
there are sentence/utterance level supersegmentals (such as pitch contour)
which differ from language to language. Clearly, Macintalk is designed to
handle American English; trying to modify it to handle other languages is
possible, but reasonable results will only happen with an holistic approach.
Also, don't forget that the Reader program would have to be modified to
correctly translate a foreign language's orthography to a phoneme string.
Regarding your second comment about Apple's lack of support for Macintalk,
alas this is true. Apple does not want to support Macintalk because they
don't have source code. When we originally contracted with Apple, they were
offered an exclusive and source code license which they declined. Now they
complain. We (Mark Barton and I, the authors of Macintalk) are currently
talking to Apple regarding an arrangement whereby we will support Macintalk.
Hopefully, we can come to some deal on this as I personally would like to see
Macintalk fully supported.
To those of you out there trying to get Macintalk to speak a foreign language,
I wish you luck, but remember: the phoneme inventory is a very small part of a
language. The real work is in developing the necessary phonological rules to
handle transitions, durations, phoneme transformations, pitch contour, etc,