What term means 'with an added octave' in musical expression?

The term that means 'with an added octave' in musical expression is "Col." This term is derived from the Italian word "col," which translates to "with" or "together," and is often used alongside indications for how to play music, particularly in combination with an added octave.

In musical notation, "col" can serve to indicate that a specific section should be performed with a particular quality or technique, which may include playing an octave higher than notated, providing a richer and fuller sound. This understanding is essential for musicians to interpret scores accurately and convey the intended emotional and dynamic qualities of a piece.

The other terms listed refer to different aspects of musical expression. "Con moto" implies a movement that should be lively or animated, "Coll'" is short for "con," meaning "with" in many contexts but does not specifically denote an octave, and "Con brio" translates to performing a piece with vigor or spirit. Therefore, these terms do not convey the concept of adding an octave, highlighting why "Col" is the appropriate choice in this context.