Think before you speak! The thoughtful voice is contemplative and considerate. It is reflective and attentive. Yes, it can sometimes be quiet and calm, but every word uttered is deep and full of wisdom, almost as if every thought goes through a reflective process.
The thoughtful voice is designed to lead an audience to a predetermined thought. Here's the trick though, each word is carefully thought out so that the audience is slowly drawn in. It pays attention to the audience's needs, while feeding them information, making them reason and helping them come up with their own thought process.
This voice often provokes an atmosphere of insight, deliberation, and thought in the audience, forcing them to think. It is effectively used in commercial spots to give obvious clues to the information you are trying to relay, and yet letting the audience make their own conclusions. The thoughtful voice is used in training videos, audiobooks, and documentaries.
Delivery of a thoughtful voice should be in a slow, measured tone to give the audience time to process the thoughts and ideas you want them to think about. It builds an atmosphere of trust, leading the audience to relate the message to their experiences.
Making an audience meditate on a subject, especially one they did not care about before, takes a masterful selection of tone and pace of delivery. You need to strike the perfect balance between opinionated and neutral. The trick is to let the audience come to your conclusion but on their own terms.