Answer:
The narrator's voice can be described as enthusiastic; encouraging
Explanation: This is an exclamatory sentence, which automatically makes you think of something urgent and upbeat. Using context clues you can guess that somebody (depending on the text) is encouraging Louis to "play", or participate in something (again, depending on the text). A detail you would need to look for in the text is something having to do with Louis playing, or more encouragement from the narrator toward Louis. It would be easier if I had the text, but use this as a guideline to answer.