My husband thought of this idea and I’m rolling it out to students in my studio. For all the songs learned by the student so far, the book and number are written on a medium size wooden bead using a Sharpie pen. Each time the student learns a new song, a new bead is added to the collection. Every day the student practices, they randomly select two beads from a draw string bag containing the beads and play them. This way favorites and not favorites are reviewed and not forgotten.