Simplify the following text for a Grade 9 native English-speaking person.
Original: Since some ocarinas are fully chromatic and can be played in professional musical situations , including classical and folk , sheet music is an ideal notation for ocarinas .
Simplified: In the 19th century , groups of ocarina players , with different sized ocarinas , played classical and folk music . Italian ocarinas became known throughout the world , because of this .