A fretless stringed instrument belonging to the extended zither family, produced in America in response to the rapid increase in popularity of Hawaiian music during the 1920s and continuing to be produced until the 1950s.

The tremoloa simulates the tonal effects of the Hawaiian steel guitar by passing a weighted roller stabilised by a swinging lever termed a bar or arm, along a melody string and creating a tremolo, an effect which also gives rise the instrument's name. The instrument also possesses 4 chords, to strum out the harmony.