How does Sinfonia work?

Keep in mind, Sinfonia is an instrument. It is meant to be played and performed over the course of the show. It is not a playback device like a tape deck or CD player. The most basic way to play Sinfonia is through the "Play" keys. By fingering the play keys, as you would a piano, at your desired tempo, you propel the song according to your individual interpretation. The process is analogous to conducting in the traditional sense; as you beat time, Sinfonia responds. You can speed up and slow down to follow the performance, moreover, you can create deep rubato passages or taut accelerandos. 'Playing' is the essential way to breath life into Sinfonia. So for starters, try using the play keys to perform some songs.