Collegiate a cappella (or college a cappella) ensembles are college-affiliated singing groups, primarily in the United States, and, increasingly, the United Kingdom and Ireland, that perform entirely without musical instruments. The groups are typically composed of, operated by, and directed by students. In the context of collegiate a cappella, the term a cappella typically also refers to the music genre performed by pop-centric student singing groups. Consequently, an ensemble that sings unaccompanied classical music may not be considered an a cappella group, even though technically it is performing a cappella. According to the nonfiction book Pitch Perfect, a cappella music is one of the oldest forms of music in existence, "the kind made without any accompaniment at all," and descended from the tradition of Gregorian chant. A cappella music as a form joined this early form with a later Puritan style, known as shape-note singing, which further extended into the American Gospel tradition. Further permutations leaked into the American pop landscape. Today, by some accounts, there exist as many as “twelve hundred collegiate a cappella groups in the United States alone.” History The RPI Glee Club of Rensselaer Polytechnic Institute, established in 1873, was one of the earliest known collegiate a cappella groups. The longest continuously-operating group is thought to be The Whiffenpoofs of Yale University, which was formed in 1909 to create a musical group with a more "modern" sound than that of the Yale Glee Club, and named for the lyrics to Little Nemo, a popular Broadway song at the time. Such names, normally intended for comedic effect, have come to define in some part the irreverent attitude found in modern collegiate a cappella. For example, the second-oldest continuously performing a cappella group (and oldest all-male group) is Yale's Society of Orpheus and Bacchus, or "SOB's". The first a cappella groups at other American Ivy League Universities include Notes and Keys of Columbia, which were founded in 1909, the same year as the Whiffenpoofs; the Princeton Nassoons (c.1941); the Dartmouth Aires (1946); the Harvard Krokodiloes (1946); Cayuga's Waiters of Cornell University (1949); and the Jabberwocks of Brown University (1949). The Vassar College Night Owls (1942) are the oldest continuous soprano/alto a cappella group. The Night Owls are a jazz ensemble who perform in all-black clothing. The Night Owls maintain over 40 orally-taught arrangements, some dating back to the founding members. In recent years, online a cappella communities have