First person narratives

Now... as example the following books...

• Jane Eyre
• PG Wodehouse's Jeeves series
• The Time travellers wife
• Memoirs of a Geisha
• Catcher in the rye
• The Eyre Affair
  

...these are all first person narratives.
Secondary characters strictly all speak through the main character.
Here's the question: Should they sound like it?
Now if you were making a movie of one of these books it would be more than a single character sitting in a room talking to the camera so my initial impulse was 'Hell No!'
A little reflection has tempered that to 'Largely No!' Audiobooks are a medium in their own right and have their own artistic code.
More on this tomorrow but for now ta-ta