Simplify the following text for a Grade 10 native English-speaking person.
Original: The New York Philharmonic is the oldest symphony orchestra in the United States which still exists , and one of the most famous orchestras of the world .
Simplified: The New York Philharmonic ( officially the Philharmonic-Symphony Society of New York ) is a symphony orchestra based in New York City in the United States . It is one of the American orchestras commonly referred to as the `` Big Five '' .