Performer emphasizes a tone by playing it more loudly than the tones around it is called?

forte (dynamics)

Explanation:  In music and musical performance, the levels of volume are called dynamics, whether it's an instrument or voice making the sound/tone. Most musical terms printed on music are in Italian. Among the loudest dynamics are mf, which means mezzo-forte (moderately loud), f, which means forte (loud), ff, which means fortissimo (very loud, louder than f), and fff, which means fortississimo (extremely loud, louder than ff). If the performer is singing, then here is an example to help you better understand dynamics: f would be louder than speaking, ff would be like speaking very loudly, and fff would be more like yelling. All of these measurements are relative to the other musicians performing around the ones who are making specific tones/notes/musical passages stand out as loud.