Orpheus/en
Orpheusis an automatic composition system and service developed by the Department of Mathematical Engineering and Information Physics, University of Tokyo.The name comes from Orpheus, the master of the lyre in Greek mythology.[1]
Overview
Input lyrics, edit settings on its structure, rhythm or chord progression, and the computer will generate a song that matches the lyrics.
Since it was easy to use (you can click a button and make a song), convenient (you can not only listen to the song but also download mp3 / midi), and versatile (change settings and you can make songs with a variety of moods and quality), many used it to create hundreds of songs after it became famous in Nan-J.
See also; Pakasong
It works by "analyzing the rhythm and pitch, and finding the melody that sounds the most natural."