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 assists a listener to tune his or her radio to the correct frequency of the station. This is because most older and cheaper radio receivers do not have digital frequency readout.
- 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 practice 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 USA, where jingles were used as identification.
Broadcasting services and interval signals
- BBC World Service: Bow Bells (English programme), Lillibullero, three notes tuned B-B-C (non-English programme, non-Europe), four notes tuned B-B-B-E (non-English programme, to Europe).
- 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.
- Ö1: Three notes tuned O-R-F by Werner Pirchner, played on viola.
- Radio Belarus: Radzima maja darahaja ("My dear Motherland").
- China National Radio, China Radio International: Chime version of 义勇军进行曲 ("March of the Volunteers").
- Voice of the Strait News Radio: Bell version of 三大纪律八项注意 ("Three Rules of Discipline and Eight Points for Attention") (Military anthem of China )
- Radio Habana Cuba: Melody of La Marcha del 26 de Julio ("March of the 26th of July") 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 Tsopanakos (Little Shepherd), played on floghera. 
- All India Radio: A tune composed by Walter Kaufmann or Thakur Balwant Singh, used since 1936.
- Radio Republik Indonesia: Rayuan Pulau Kelapa ("Solace on Coconut Island"), composed by Ismail Marzuki.
- Radio Japan:
Kazoe-uta (Japanese counting song)
さくらさくら ("Sakura Sakura" - Cherry Blossoms).
- Voice of Korea: Melody of 김일성장군의 노래 ("Song of General Kim Il-sung").
- Pyongyang FM - Melody of 김정일장군의 노래 ("Song of General Kim Jong-il")
- KBS World Radio: Dawn.
- RTL Radio: Feierwon by Michel Lentz, played on chimes.
- Voice of Mongolia: Эх орон ("Motherland").
- Radio New Zealand International: The call of a New Zealand bellbird.
- Radio Pakistan:
- Far East Broadcasting Company: Lord Jesus to Save Sinners.
- Radio Veritas Asia: O via, vita, veritas
- RTÉ Radio 1: Chime version of O'Donnell Abú ("O'Donnell Forever").
- Radio Romania International: Pui de lei by Ionel G. Brǎtianu
- Radio Slovenia: Electronically generated cuckoo chirping.
- Radio Ukraine International: Реве та стогне дніпр широкий (The roaring and groaning Dnipro is wide).
- WEWN, later EWTN Global Radio: Salve Regina
- National Broadcasting Company: 3 chime-like notes.
- Trans World Radio: What a Friend We Have in Jesus.
- Voice of America: Brass band version of Yankee Doodle.
- Vatican Radio: Christus Vincit, played on celesta.
- Radio Nacional de Venezuela - Canal Internacional: Beginning of Alma Llanera by Pedro Elías Gutiérrez and Rafael Bolívar.
- Radio Australia: Chimes version of Waltzing Matilda (chorus). News signature tune: Majestic Fanfare.
- Radio Netherlands: Carillon version of the Eighty Years' War song Merck toch hoe sterck.
- BBC World Service: Trumpet version of Oranges and Lemons, first four notes of Symphony No. 5 by Beethoven, played on timpani; Lillibullero (signature tune, played on trumpet).
- Radio Tirana: Këputa një gjethe dafine (transmission intro) and the trumpet version of With Pickaxe and Rifle.
- Radio Austria International: Orchestral version of An der schönen blauen Donau ("Blue Danube Waltz") by Johann Strauss.
- RTBF International: Où peut-on être mieux qu’au sein de sa famille.
- Rádio Nacional: Luar do Sertão.
- Radio Peking (predecessor of China Radio International): Chimes version of 东方红 ("The East Is Red").
- Cyprus Broadcasting Corporation: Avkoritsa by Andreas Mappouras, played on guitar
- Radio Prague:
Trumpet version of Kupředu levá ("Forward, Left") by Jan Seidl
Adagio – Allegro molto from Symphony No. 9 by Dvořák.
- Radio Finland: Pim-pam-pulla by A. O. Väisänen.
- Radio France Internationale: Trumpet version of a popular song Nous n'irons plus au bois.
- Berliner Rundfunk: Motif from the opera Regina by Albert Lortzing, played by trumpets.
- Radio Berlin International: Beginning of Auferstanden aus Ruinen ("Risen from Ruins"), played on chimes.
- Radio DDR: First few bars of Wann wir schreiten Seit’ an Seit’.
- Deutschlandfunk: Celesta version of Dir, Land voll Lieb' und Leben from "Ich hab mich ergeben" by Hans Ferdinand Maßmann.
- Radio Budapest: Excerpts from the suite 1848 by T.K. Polgar played on 3 trumpets and 2 cornets.
- Kol Yisrael: Trumpet and drum version of Hatikvah.
- Rai Italia Radio: Mechanically generated canary chirping.
- Trans World Radio: Hymne Monégasque
- NPO: First seven notes of Wilhelmus, played on clarinet (Radio 1 and Radio 5), synthesizer (Radio 3), spinet (Radio 4) and carillon (Radio 2).
- NRK P1: Motif from Sigurd Josarfal by Edward Grieg.
- Radio Norway International (former international service of NRK): Ancient folk tune from the Hallingdal region and
- Radio Katowice: Sound of a hammer striking an anvil.
- Polish Radio External Service: Excerpt from Prząśniczka by Stanisław Moniuszko, played on piano.
- Radio Polonia: Piano version of Etude No. 12 ("Revolutionary Etude") by Frédéric Chopin.
- Radio Sweden: Chime version of Ut i vida världen ("Out in the Wide World"), composed by Ralph Lundsten and the opening notes of Carl Michael Bellman's Storm och böljor tystna r'en..
- Radio Bucharest 1 and Radio Bucharest External Service (pre-1989): Fragment from Cantata anilor luminǎ by Anatol Vieru
- Radio Canada International: First four notes of O Canada, played on piano or autoharp.
- Radio Mayak: Vibraphone version of Moscow Nights.
- Voice of Russia: "Majestic" chorus from the "Great Gate of Kiev" portion of Pictures at an Exhibition by Mussorgsky.
- Radio Serbia: Bože pravde.
- Radio Slovakia International: Kto za pravdu horí.
- Radio RSA (former international service of Apartheid-era South African Broadcasting Corporation): Bokmakierie chirping and first bars of Ver in die Wereld, Kittie, played on guitar.
- Radio Beromünster: D' Zit isch do, played on music box.
- Swiss Radio International: Lueget, vo Berg und Tal.
- Voice of Turkey: Makam, played on piano.
- Radio Moscow (former international service of the Soviet Union):
Песня о Родине ("Wide Is My Motherland")
Midnight in Moscow, played by balalaika.
- WYFR: First two bars of To God Be the Glory by William Howard Doane played by brass band
- Radio Yugoslavia (1980-1989): First bar of Druže Tito,ljubićice bjela anonymous Partisan song, in various orchestral renditions 
- Radio Yugoslavia, later International Radio of Serbia and Montenegro: Jugoslavijo by Nikola Hercigonja.
- NWDR: The 4th symphony by Brahms.
Classical Radio Station WQXR-FM in New York City, during its ownership by The New York Times Company, played different variations of a classical infused gong with the ID read at the same time as "The Classical Station of the New York Times, WQXR, New York (And WQXR.com 2000-2009)
Numbers stations interval signals
- Ö1 gehört gehört, p. 218.
- Tuning into broadcast history. The Hindu BusinessLine, 15 October 2015.
- BBC World Service (Europe) interval signal Retrieved 2013-10-09.
- Frost, J. M. World Radio TV Handbook. New York: Billboard Publications, 1983.
- nl:Pauzeteken[better source needed]
- Frost, Jens Mathiesen. World Radio-TV Handbook. London: Billboard Publications, 1974.
- Radio Sweden interval signal Retrieved 2011-11-24.
- DX LISTENING DIGEST 7-043