And in applications like text-to-speech/speech synthesis and speech recognition. Then there are the gray areas like training statistical models that are not ML

And in applications like text-to-speech/speech synthesis and speech recognition. Then there are the gray areas like training statistical models that are not ML/ANNs, but are things like Hidden Markov Models and the Vertibi algorithm. While not using ANNs, they work in a similar way in that they are statistical models trained on a large corpus of data, and those models are then used to predict various things like the part of speech, end of a sentence, or the pitch of a phoneme.