What is it about music that makes it so hard to describe? The basic elements of music are almost mathematical in principle, with each instrument carefully added and subtracted in order to equate to a successful composition. Despite the simplicity of the formula, bands with similar levels of talent and potential fare far better than others. So, what decides whether or not a band will make it?

Take, for example, a band I saw in concert last week called Local Natives. As relative newcomers to the scene, Local Natives found fame following the release of their debut album Gorilla Manner in February of 2010. Their composition relies heavily upon vocal harmonies and layered instrumentation, both of which require extraordinary precision. A single missed note or poorly timed drum stroke could compromise the success of their entire musical equation, yet there is something that protects their performances from this threat. Perhaps it is their youthful enthusiasm or contagious energy (or maybe something else entirely) that has allowed them to ignore the risks and find success. Whatever it is, though, is difficult to find and even more difficult to achieve.

The Head and the Heart, another fledgling band from the west, shares a similar sound with Local Natives, yet they have not shared the same success. While the members of the Head and the Heart are gleaning more attention thanks to a recent feature on NPR, their journey toward fame has lacked the momentum of Local Natives. Despite the similar incorporation of harmonization and instrumental textures, their musical equation hasn’t matched the outcome of their contemporaries. While they lack neither talent nor potential, the Head and the Heart need to work on their magnetism. Again, that ineffable sense of energy acts as the variable in the equation for success.

These musical doppelgangers are not rare. Mumford & Sons debut album, “Sigh No More,” catapulted the band to fame while their lesser known musical doppelgangers, a band called Stornoway, remain relatively unknown in the states.

In some ways, this disparity in success seems unremarkable. Success, failure and stagnancy are not restricted to the world of music; we see it every day in college admissions, job interviews and even friendships. The difference, however, lies in the fact that music fans can feel the reason behind the success. When we go to shows, we expect to feel that indescribable energy and magnetism that separates good bands from great ones. This feeling is not restricted to acts that have already found fame. In fact, it’s almost better when you find it in an opening act or an unknown band. Just as with every piece of art, there is a sense of familiarity within the innovation. This familiarity allows us each to return to a state of vulnerability, making it possible for the music to permeate our senses and resonate with our emotions.

While these elements are certainly a factor what is good and what is great, there are other variables that complicate the equation. This is where the beauty of the x-factor comes in; there is no correct value for these variables. Each band must find the ones that work for them and, ultimately, the ones that work for their fans.