Numbers 10:1-18, have been made in recent years and used in prayer services at the Western Wall. In the United States Peter Christian Lutkin, dean of the Northwestern University School of Music, helped popularize a cappella music in the United States by founding the Northwestern A Cappella Choir in 1906. The A Cappella Choir was "the first permanent organization of its kind in America." An a cappella tradition was begun 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 tradition of a cappella choral music was born in the region at colleges like Concordia College (Moorhead, Minnesota), Augustana College (Rock Island, Illinois), Waldorf University (Forest City, Iowa), Luther College (Decorah, Iowa), Gustavus Adolphus College (St. Peter, Minnesota), Augustana College (Sioux Falls, South Dakota), and Augsburg University (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. Movements in modern a cappella over the past century include barbershop and doo wop. The Barbershop Harmony Society, Sweet Adelines International, and Harmony Inc. host educational events including Harmony University, Directors University, and the International Educational Symposium, and international contests and conventions, recognizing international champion choruses and quartets. Many a cappella groups can be found in high schools and colleges. There are amateur Barbershop Harmony Society and professional groups that sing a cappella exclusively. Although a cappella is technically defined as singing without instrumental accompaniment, some groups use their voices to emulate instruments; others are more traditional and focus on harmonizing. A cappella styles range from gospel music to contemporary to barbershop quartets and choruses. The Contemporary A Cappella Society (CASA) is a membership option for former students, whose funds support hosted competitions and events. A cappella music was popularized between the late 2000s and the early to mid-2010s with media hits such as the 2009–2014 TV show The Sing-Off and the musical comedy film series Pitch Perfect. Recording artists In July 1943, as a result of the American Federation of Musicians boycott of US recording studios,