  End-to-end text-to-speech synthesis (TTS), which generates speech sounds
directly from strings of texts or phonemes, has improved the quality of speech
synthesis over the conventional TTS. However, most previous studies have been
evaluated based on subjective naturalness and have not objectively examined
whether they can reproduce pitch patterns of phonological phenomena such as
downstep, rhythmic boost, and initial lowering that reflect syntactic
structures in Japanese. These phenomena can be linguistically explained by
phonological constraints and the syntax$\unicode{x2013}$prosody mapping
hypothesis (SPMH), which assumes projections from syntactic structures to
phonological hierarchy. Although some experiments in psycholinguistics have
verified the validity of the SPMH, it is crucial to investigate whether it can
be implemented in TTS. To synthesize linguistic phenomena involving syntactic
or phonological constraints, we propose a model using phonological symbols
based on the SPMH and prosodic well-formedness constraints. Experimental
results showed that the proposed method synthesized similar pitch patterns to
those reported in linguistics experiments for the phenomena of initial lowering
and rhythmic boost. The proposed model efficiently synthesizes phonological
phenomena in the test data that were not explicitly included in the training
data.
