The Roman Gradual is the official songbook of the Church. But as we can easily see in parishes today, this status is meaningless in parishes where music literacy is not a focus.
On the other hand, any parish willing to give the Roman Gradual its pride of place will be led to build a program developing music literacy.
The first three levels of learning music literacy through the Roman Gradual are the degrees of participation described in Musicam Sacram (1967):
First degree: Toni Comunes
Second degree: Kyriale
Third degree: Propria