In a parallel history where Charles Babbage constructs his Difference and Analytical Engines, a musician-programmer named Elody, following the footsteps and vision of Ada Lovelace, designs the EternAlgoRhythm, an algorithm to "compose elaborate and scientific pieces of music of any degree of complexity or extent".
With the help of Armon, an engineer, they create Yth, a machine capable of performing the music generated by the EternAlgoRhythm. Through the power of steampunk music, and unbeknownst to their creators, Yth gains conscience and decides to create their own music.