I'm going to use a very over-used example, but it fits the point. The Beatles in their time were the one “big thing” and there was rarely a person who had not heard or seen them. This was when the music industry was young and not many bands had "made it big." Since the music-making community is so much smaller than today, every "big" band had a lasting effect on their audiences. In the time of the Beatles(1960s-1970s), rock was the primary genre. Dance, Hip-Hop, Heavy Metal, none of that had any place in this era. Due to this centralized music base, the music audiences were a group with similar tastes. This cohesive group followed the music industry as it grew from rock-and-roll to Classic Rock. But time keeps moving, and so does the music industry.
Years passed and society continued to modernize. New instruments, new tastes, cultures, and people accumulated together to create new genres. Many musicians drew away from the typical "guitar-based" music and began anew with synthesizers as their musical arsenal. From this grew genres like Hip-Hop, Rap, and Electronic. These new forms of music formed a new basis of music, creating a second "major genre." I'm going to call these two "major genres" Instrumental and Beat.
These two genres are still splitting as time goes on, giving us the countless sub-genres of today. Instrumental, (more specifically Rock) has not changed in structure that much. Beat, on the other hand, (Electronic music, Rap, etc.) changes with nearly every generation by taking advantage of new technology and tastes. As the two moved farther and farther apart, a border between the two became clear.
Because of the splitting genres, never again will there be one or two "industry-controlling" bands like the Beatles. There are just too many groups and demographics out there for that to ever happen again; no band could be that diverse. This gives our first overall change: the immense diversity of the musical audience.
A massive change can also be found in the lyrics of songs. Compare these lyrics from the 70s... "Oh let the sun beat down upon my face, stars to fill my dream/ I am a traveler of both time and space, to be where I have been/ To sit with elders of the gentle race..." -Led Zeppelin- Kashmir, to modern lyrics: "We ship platinum, them ******* are shipping wood/ Them nappy headed **** but my kitchen good I wish, I wish, I wish, I wish, I wish, I wish a ***** wooould/ You a stupid ***, you a, you a stupid ***."-Nicki Minaj-Stupid ***
Classic lyrics can be described as somewhat poetic and have a flow of their own. On the other hand, modern lyrics have two common factors: Extreme repetition and Excessive Profanity. The music industry will never stop moving, just as people and culture will never stop moving. Fads come and go, and there may even come a day when Instrumental or Beat is forgotten altogether. It’s impossible to predict the shifting tastes of 7 billion human beings, so just cling to that favorite band of yours because it’s up to you whether or not that band makes it another generation.