An interval signal, or tuning signal, is a characteristic sound or musical phrase used in international broadcasting, numbers stations, and by some domestic broadcasters, played before commencement or during breaks in transmission, but most commonly between programmes in different languages.
It serves several purposes:
It helps a listener using a radio with an analog tuner to find the correct frequency.
It informs other stations that the frequency is in use.
It serves as a station identifier even if the language used in the subsequent broadcast is not one the listener understands.
The practise began in Europe in the 1920s and 1930s and was carried over into shortwave broadcasts. The use of interval signals has declined with the advent of digital tuning systems, but has not vanished. Interval signals were not required on commercial channels in the United States, where jingles were used as identification.
Radiodifusión Argentina al Exterior: First eight notes of "Mi Buenos Aires querido" by Carlos Gardel, followed by people saying the station's name in eight languages.
Radio Belarus: "Motherland, my dear" (Радзіма, мая дарагая) by Vladimir Olovnikov and Ales Bachyla.
China National Radio and China Radio International: Chime version of March of the Volunteers (义勇军进行曲).
Voice of the Strait News Radio: Bell version of "Three Rules of Discipline and Eight Points for Attention" (三大纪律八项注意).
Radio Habana Cuba: Melody of "March of the 26th of July" (La Marcha del 26 de Julio) by Agustín Díaz Cartaya.
DR P1: "Drømte mig en drøm i nat", played on xylophone.
Radio France Internationale: Electronic-disco, culminating in the last 8 measures of "La Marseillaise".
Deutsche Welle: Celesta version of "Es sucht der Bruder seine Brüder" from Fidelio by Ludwig van Beethoven.
Voice of Greece: "The Little Shepherd" (Ο Τσομπανάκος), played on floghera.
All India Radio: A tune composed by Walter Kaufmann or Thakur Balwant Singh, used since 1936.
Radio Republik Indonesia: "Solace on Coconut Island" (Rayuan Pulau Kelapa), composed by Ismail Marzuki.