Read this: A strong and prominent a cappella tradition was begun in the midwest part of the United States in 1911 by F. Melius Christiansen, a music faculty member at St. Olaf College in Northfield, Minnesota. The St. Olaf College Choir was established as an outgrowth of the local St. John's Lutheran Church, where Christiansen was organist and the choir was composed, at least partially, of students from the nearby St. Olaf campus. The success of the ensemble was emulated by other regional conductors, and a rich tradition of a cappella choral music was born in the region at colleges like Concordia College (Moorhead, Minnesota), Augustana College (Rock Island, Illinois), Wartburg College (Waverly, Iowa), Luther College (Decorah, Iowa), Gustavus Adolphus College (St. Peter, Minnesota), Augustana College (Sioux Falls, South Dakota), and Augsburg College (Minneapolis, Minnesota). The choirs typically range from 40 to 80 singers and are recognized for their efforts to perfect blend, intonation, phrasing and pitch in a large choral setting.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): What do a capella choirs struggle to perfect in a large choral setting?
unanswerable