This is one of the most obvious things in notated music: It's a piece of cake; you can see it right away. So what difference can it possibly make?
Well, the ear seems to care a great deal about the difference between rising and falling. So much so that for many years falling meant sadness and rising meant joy. Then comes a tune like Joy to the World, which goes in altogether the wrong direction. But that's Handel--announcing this great good news by turning acoustical logic upside down.
(Actually another example, far less meaningful, but still: London Bridge is Falling --- should be up! This was one of the examples from a wonderful children's book popular about 50 years ago called The Silly Book.)
When we hear a single tone without accompanying chord it is fairer to expect it to rise than to fall. We take the tone to be a fundamental, especially if it is centrally placed within the vocal range, G for example. This is why the opening G of Mozart's G Minor Piano Quartet is so deeply unsettling: It goes down to D rather than up, thus establishing D as a more secure tone. Did Mozart know this? How could he not? The theme is identical to that of the early G major, actually minor piano and violin sonata except that in that piece the D is a 5th above not a 4th below the G.
Just because we know where the proper sounds are located on our instruments doesn't mean we have processed them in terms of their resonance within tonal space.
