I've been fortunate to see my daughter play Tobias in Sweeney Todd twice, once with a small professional company that performed the show in an actual pie shop. (The restaurant was two levels with a spiral staircase that had a platform, and they managed to fit about 60 seats for an audience. It was so fun.)
Anyway, the company spent a full month of rehearsal just on the music and harmonies before any blocking. It's probably the hardest she was ever pushed at the time musically.
She never complained once. That's the power. Even when it was work - hard, long, grueling work, and even more of it at home - the material was so good it never, ever felt like it to her.