It seems to me that the retort is missing the main point of Nikhil's essay. Nikhil wrote about the concept of associating a single song with a part of one's life, not trying to actually "encapsulate the entire experience." In other words, Nikhil was not trying to suggest that a single song is able to accurately represent a person's entire journey. Instead, Nikhil was simply referring to the idea of picking out a meaningful piece of music that reminds one of a specific period of time. It's true that music is often used as a coping mechanism to try and make sense of the world, but Nikhil doesn't actually argue this in his essay.
Furthermore, music could be said to represent certain emotions and memories without actually reflecting an entire period of life. The correlations between music and emotion make it possible to access a certain moment in time with the right piece of music. While two people may not necessarily experience the same emotion when they hear the same song, they still can both be reminded of a certain moment or experience by listening to it. Therefore, it is possible to associate a single song with a part of one's life.
In conclusion, although Nikhil wasn't trying to suggest that a single song can accurately represent a person's entire journey, his original essay still stands as an accurate representation of how one might choose a song to help bring back memories of a certain time period. Therefore, to suggest otherwise would be UrRong! Just remember that the next time you hear your favorite song from your teenage years, it probably means you're getting old.