Oom-pah, Oompah or Umpapa is an onomatopoeic term describing the rhythmic sound of a deep brass instrument in combination with the response of other instruments or registers in a band, a form of background ostinato.^[1][2]

The oom-pah sound is usually made by the tuba alternating between the root of the chord and the 5th — this sound is said to be the oom. The pah is played on the off-beats by higher-pitched instruments such as the clarinet, accordion or trombone. Oompah is often associated with Volkstümliche Musik, a form of popular German music, and with polka. In triple time genres such as the waltz it is oom-pah-pah.

The musical Oliver! contains a song named "Oom-Pah-Pah", which is named after the oom-pah.

A more modern variation is the playing of contemporary pop and rock songs in an Oompah style, by bands such as Global Kryner (Austria), Brumpah (UK Westmidlands) ^[3] and Oompah Brass (UK) (who dubbed the style "Oompop").^[4] The American jam band Phish features the oom-pah-pah in their song "Harpua".