A method and apparatus include receiving a text input that includes a sequence of text components. Respective temporal durations of the text components are determined using a duration model. A first set of spectra is generated based on the sequence of text components. A second set of spectra is generated based on the first set of spectra and the respective temporal durations of the sequence of text components. A spectrogram frame is generated based on the second set of spectra. An audio waveform is generated based on the spectrogram frame. The audio waveform is provided as an output.