First, I want to clarify one thing. While the mention of music theory may seem intimidating to the emerging musician, it doesn’t necessary refer to the studies of fugue or species counterpoint.
And while countless bands have put out tons of music in the past 70 plus years of mainstream music with little to no formal music education, the techniques employed by these said artists generally DO tend to follow the concepts studied in music theory whether they know it or not.
This said, I generally tend to answer the above question by directing the benefits of applied music theory toward a discussion of its practicality in the mainstream rock and pop ensemble. This ensemble being one comprised of guitar, bass, drums, and vocals.
As an example, many guitarists tend to get by just fine playing only open chords on the first three frets of the guitar and power chords. But if a player can learn how to spell and construct chords, they will discover that the same shapes found in open chords may be played anywhere on the fretboard to produce alternate voicings of the same chords found in the open position.
While the obvious benefit of being able to form chords throughout the fretboard is more options in which to produce different voicings of chords in different registers, the real benefit is actually in the ability to employ the use of keys other than A, C, D, E, and G; which open chords alone tend to suggest.
Following this, should both the bass player and guitar player learn to spell and construct scales, and the chords diatonically occurring within the scale, both players will be able to further elaborate on musical ideas when playing lead or accompanying melodies.
With regards to rhythm, the only essential element to music, yet oddly enough, what seems to be the most neglected fundamental of music, our studies of music theory suggest there is a multitude of different meters to choose from. However, in today’s music we typically only hear 4/4 and 2/4, while other excellent alternatives such as ¾ (Led Zepplin’s Kashmir), 6/8 (Metallica’s Nothing Else Matters), and 7/4 (Pink Floyde’s Money) do exist, yet are vastly out numbered by the predominantly over-used time signatures of 2 and 4.
Where this all becomes really interesting is in the contribution of each player to the collective sound of the ensemble. As the roll of the bassline is to color the drumbeat so as to resonate with the harmony, the harmony exists to connect the combination of drums and bass to the melody, which in turn connects the instrumentation of the ensemble to the lyricism.
And as a band is the product of these contributions from players, should these players further come to understand the inner workings of music, and thus their respective parts, an ensemble can break away from traditional formulas of popular music and push the envelop that is the caliber of musicianship within the band.
~ Mr Greg