Musical Allusions 6 by AlexanderD

Question 12

An Elvis standard, an Elvis sub-standard, a song associated with the US Military Academy, and a song Ted Mosby sang with Will Shortz on "How I Met Your Mother" all have the EXACT SAME MELODY as what Civil War tome about a maiden written by George R. Poulton & WW Fosdick that sounds like directions on how to take medicine?

Aura Lea