Harp bells offer a mellow contrasting voice to the generally strident authentic voice of cast bronze bells. Generally a metalophone using tuned bars of aluminum or other alloys is struck with relatively soft mallets rather than hammers made of metal.
Carillonists often use mechanical practice keyboard instruments equipped with harp bells for two reasons. First, the public is not subjected to repeated performance of difficult passages, and secondly the mellow voice of the bells allow hours of practice without excessive hearing fatigue caused by authentic bells. The following video depicts Nora Johnston, sister of bell founder Cyril Johnston, playing such an instrument in order to improve dairy milk cow production.
Large organs, most theatre organs in particular, will often include both chimes and harp bells. Electronic chime and carillon systems offer the option to play harp bell voicings to accompany chime melodies, such as the Chime Master Concert Chime with Harp Bells voice.