Discuss why two people with similar abilities may have very different expectancies for performing at a high level.

Because they're two different people

Explanation:

The main and major reason why, is the obvious one. The first reason that comes to the mind.

Because they are two different people. Different people have different goals, hopes and aspirations. And even those that share them go through different paths while carrying them out. The minds of the two individuals are not the same, and despite the fact that they have similar abilities, they might not necessarily get the job done on time because of other commitments either of them have. Even if they both have none, there's always a distinguishing factor, and that will always trump, thus making them have different expectancies for performing at a high level.

among other factors, composers started writing dynamic markings in their scores because "new instruments allowed for more dynamic ranges and contrast."

dynamics allude to the loudness or softness of music. dynamics offer an approach to demonstrate articulation in sheet music. they to drive the enthusiastic substance of music through volume and force. maybe you could alter both the volume and the shading profundity on your screen at the same time. we can likewise think about the force side of elements as the quality of a note. a few notes are intended to be played delicately and gently, while others are intended to be played all the more firmly.  

some dynamics markings have a letter 'm,' which remains for mezzo, signifying 'medium.' so a mezzo piano unique stamping resembles this (mp) and intends to play medium calm, while a mezzo specialty dynamic resembles this (mf) and intends to play medium loud.