  Despite previous efforts in melody-to-lyric generation research, there is
still a significant compatibility gap between generated lyrics and melodies,
negatively impacting the singability of the outputs. This paper bridges the
singability gap with a novel approach to generating singable lyrics by jointly
Learning wOrding And Formatting during Melody-to-Lyric training. After
general-domain pretraining, our proposed model acquires length awareness first
from a large text-only lyric corpus. Then, we introduce a new objective
informed by musicological research on the relationship between melody and
lyrics during melody-to-lyric training, which enables the model to learn the
fine-grained format requirements of the melody. Our model achieves 3.75% and
21.44% absolute accuracy gains in the outputs' number-of-line and
syllable-per-line requirements compared to naive fine-tuning, without
sacrificing text fluency. Furthermore, our model demonstrates a 63.92% and
74.18% relative improvement of music-lyric compatibility and overall quality in
the subjective evaluation, compared to the state-of-the-art melody-to-lyric
generation model, highlighting the significance of formatting learning.
