The song is varied and improvisatory, an irregular stream of rough and whistling phrases, trills and snatches of imitations of other bird species. It is often rendered as "tjerr-tjerr-lili-tjerr" with constantly shifting tempo and pitch. The song is often delivered in a short display flight, where the bird rises out of the vegetation with vibrating wings and sings on its way back down. This means the Sedge Warbler at times becomes clearly visible.