Steelpan is musical instruments called a steel drum.

It was developed in island nation Trinidad & Tobago in Caribbean Sea.

Photo by '民族楽器コイズミ' in Japan.

http://www.koizumigakki.com/

To do the tremolo, long touch some note or two different notes.

Musical instruments named Mini Steelpan only of 11 music scales that

was able to be performed easily were put in iPhone/iPod Touch.