Well-performed audio narrations are a hallmark of captivating podcasts, explainer videos, radio stories, and movie trailers. To record these narrations, professional voiceover actors follow guidelines that describe how to use low-level vocal components—volume, pitch, timbre, and tempo—to deliver performances that emphasize important words while maintaining variety, flow and diction. Yet, these techniques are not well-known outside the professional voiceover community, especially among hobbyist producers looking to create their own narrations. We present Narration Coach, an interface that assists novice users in recording scripted narrations. As a user records her narration, our system synchronizes the takes to her script, provides text feedback about how well she is meeting the expert voiceover guidelines, and resynthesizes her recordings to help her hear how she can speak better.