  Melody harmonization has long been closely associated with chorales composed
by Johann Sebastian Bach. Previous works rarely emphasised chorale generation
conditioned on chord progressions, and there has been a lack of focus on
assistive compositional tools. In this paper, we first designed a music
representation that encoded chord symbols for chord conditioning, and then
proposed DeepChoir, a melody harmonization system that can generate a four-part
chorale for a given melody conditioned on a chord progression. With
controllable harmonicity, users can control the extent of harmonicity for
generated chorales. Experimental results reveal the effectiveness of the music
representation and the controllability of DeepChoir.
