When you’re supposed to read the book, but you watch the movie instead, you’re cutting corners. When you’re preparing for a test, and you’ve only read the cliff-notes, you might miss some of the details. When you’re a performer and you only listen to the cast recording in preparation for your role in a production, you’re missing a whole lot.
When I’m music directing a cast of actors I try to give everyone the benefit of the doubt. I try not to make assumptions, and respect that everyone has a different learning curve and a different process. However, there are those occasions when you want to bang your head against the wall in disbelief.
This happened once, as it sometimes does; I worked with an actor who was not prepared with their role. When I asked how this person prepared, it was clear that they had only listened to the recording; what else was needed? For one thing, the part to sing might not be the part featured on the commercial recording.
Not every cast recording is perfect. Few are. And the performers take liberties with the material that they’ve worked to create with their cast and their creative team. Listening to someone else is just hoping for a decent imitation.
Yes, listen for reference, but if we want to be our own artists, we have to work past that. In the court of law, ignorance is no excuse. The same holds for the rehearsal process; there is all due diligence expected.