The tradition of having musicians available continued and eventually grew into standard brass bands. These are still seen in public at Army campaigns, as well as at other festivals, parades and at Christmas. Across the world the brass band has been an integral part of the Army's ministry and an immediately recognisable symbol to Salvationists and non-Salvationists alike. The Salvation Army also has choirs; these are known as Songster Brigades, normally comprising the traditional soprano, alto, tenor and bass singers. The premier Songster Brigade in the Salvation Army is the International Staff Songsters (ISS). The standard of playing is high and the Army operates bands at the international level, such as the International Staff Band (a brass band) which is the equal of professional ensembles although it does not participate in the brass band contest scene, and territorial levels such as the New York Staff Band. Some professional brass players and contesting brass band personnel have Salvation Army backgrounds. Many Salvation Army corps have brass bands that play at Salvation Army meetings, although not all. The Salvation Army also fielded large concertina bands. From the turn of the (20th) century to the Second World War between a third and a half of all SA officers in Britain played concertina. For an evangelist the concertina's portability, its ability to play both melody and chords, and most especially the fact that the player can sing or speak while playing, were all distinct advantages over brass instruments.