Final answer:
Cecil Sharp was recognised for his fieldwork in collecting and preserving traditional folk music and is the correct answer to which of the four people listed sought out traditional musicians.
Step-by-step explanation:
The person known for going out into the country in search of traditional musicians is Cecil Sharp. Cecil Sharp was an English folklorist and collector of folk music and dance, renowned for his work in the early 20th century documenting traditional English and Appalachian folk songs. Unlike the other individuals listed, such as Josh Graves, Richard Greene, and Ronnie McCoury, who are notable musicians within the bluegrass and folk genres, Cecil Sharp's legacy includes extensive fieldwork and contributions to the preservation of folk music traditions.