Horace and Morris Join the Chorus (but what about Dolores?) (Horace and Morris and Dolores)

Horace and Morris, but mostly Dolores, are back again for another uproarious adventure. When the three best friends decide to try out for the school chorus together, they're shocked when Dolores (who can only sing notes that no one has ever heard before) is the only one who doesn't make the cut. After all, they've always done everything together.
Once Horace and Morris start chorus practice, they're so busy that they don't have time to go exploring or climb trees with Dolores anymore. Feeling left out and alone, Dolores decides to take matters into her own hands. But can she prove to Moustro Provolone that there's a place for every kind of voice in the chorus?