Whistles

Whistles usually refers to the range of Diatonic Penny Whistles that performers use. Being diatonic, players change key by changing whistle (in general). Also known as Tin Whistles as they are most often made of Tin Plate. These days a variety of Plastic Whistles are available. Even though they all cost considerably more than a penny and not many are now made from Tin Plate, they still retain both names. 

Whistles (i.e. like a referee's whistle) are used as effects in some tunes and they are used by some Dance Bands to signal a tune change.