Definition & Meaning of "quadruple note"

What is a "quadruple note"?

A quadruple note, also known as a longa, is a musical symbol that represents a duration of four beats in common time. It is depicted as a hollow circle with two vertical lines on either side. The quadruple note is used less frequently in modern music but was more common in earlier musical notation systems. It is used to indicate a note that should be held for a longer period compared to a whole note, making it useful for compositions that require extended note durations.