on Jane Friedman site:

So much of what makes readers respond to and love a character’s voice is steeped in emotion—from the raw and vulnerable to the fierce and confrontive. Voices that allow us to feel are often the most memorable.

However, emotion isn’t just about characters laughing or crying; it encompasses a much broader spectrum. What truly defines a character’s emotional depth is not just what they feel, but how they express it—the words they choose, the rhythm of their speech and thoughts, and the unique ways they reveal their inner world.

When it comes to consciously shaping character voice, looking at our characters’ emotional depths can help enhance voice. It’s also worth noting that a character who has little to no emotional access can still have a great voice.