In a past life, I was a music major. This prepared me to talk about music a lot. And even to produce it. But it, did not prepare me to play it. So, for the past several decades, I have been a frustrated picker, with music in my head with no way of getting out. But I am grateful fur the understanding of how music works. It has been a great help in producing all sorts of audio. And, if you understand how to hear it, you can be a much more effective video producer as well.
I'd like to post a few thoughts (over several posts) about music and how it works. Since dissonance is so important to both the enjoyment and composition of music, as well as its history and cultural implications, I would like to start there.
From a technical perspective, music is the creation and resolution of audible dissonance. Although there are several elements that go into this creation and resolution, the one that has been commonly used is harmonic sounds...usually in a modal construct. To most of us, that means chords within key structures (major, minor, blah, blah, blah).
Dissonance is in the ear of the beholder. It tends to be culturally agreed upon. And we become immune to it over time. So, we tend to have harmonies that are associated with certain time periods. For example, a seventh chord was never used (or at least never called that) during the Baroque period (1650-1750). The added blast of overtones that comes with adding an F to a G major triad would be had for the innocent ears of Baroque listeners to take. Some really smart composers would slip what we call a seventh into a chord in the form of a "passing tone" or something. Because the cutting edge is always hungry for a little more spice than the mainstream.
Over time, the mainstream catches up. And what used to be interestingly dissonant becomes white-bread. So, composers respond to demand (or anticipate it) by finding new ways to create dissonance. The classical period ushered in bigger orchestras, more complex harmonies, longer compositions (the symphony, for example), and along with the addition of more instruments came new ways of being dissonant. Also, the classical period gave us smaller ensembles (the string quartet), in which the parts of the individual players allowed for implied (gestalt) harmonies. Listen to Hayden's string quartets to see what I mean.
This marching forward of dissonance leads right through the romantic period (which is characterized by things like "chromatic harmony"Â in which a composer may be working, as far as the listener is concerned, in more than one key at a time, or may just borrow some notes from the key next door, just to make some harmonics clash). Romantic music also gave us annoying things like, descriptive compositions called "program music." This tends to be lush, annoying stuff that with titles like, "overture to some people in white shoes having a picnic."
The 20th century was a dissonance party among serious composers. Folks started looking to things like found compositions jack hammers, squirt guns, traffic noise, a basketball buzzer, all woven together into a composition), tone rows (random sequences of notes), whole tones (think about that floaty French music), quarter tone (think about Chinese music), atonal composition (intentionally resisting the pedestrian notion of key|"tonic" or resolution).
In the 20th century, we had a fork in the road, as academic and fine art composers went headlong into the dissonance jungle, while most ordinary listeners pulled back. This gave rise to folks like Aaron Copeland and George Gershwin-basically pop songwriters, film score writers, and show tune composers (albeit at a very high level) writing music for the orchestra that appealed to popular taste.
Meanwhile, folks like Bartok and Shostakovich were pushing dissonance as far as they could, trying to continue along the 400-year path of reinventing music while playing with modernist ideas like relativism, industrialism, and socialism. They made some pretty music and some ugly music. Some of it is more important than it is enjoyable.
In the world of popular music, the whole dissonance thing lags. It's probably always been the case. The pop music of today is probably equivalent to the folk music of other times and places. Folk music is, by it's nature ephemeral. It exists in a time and place and then goes away. What is left is some lyrics, a sense of instrumentation, and an idea of a performance style. So it should come as no surprise that the pop music of the past fifty years has consistently reflected harmonic styles that were already obsolete 100 years earlier. And, rather than deriving their harmonic structure from the orchestral and choral composition of their time, they tend to be derivative of other pop music. Thus, the musical family trees of...say...the Stones, Zeppelin, and The Beatles.
Occasionally, you'll find a musician who finds an innovative way of making dissonance in the way he plays his instrument, rather than through harmonic structure. Jimi Hendrix, rather than seeing feedback or distortion as something to be avoided, harnessed the random sounds and screams, building them into the music. Similar innovations were made in Jazz by players like Monk, Miles, and the Bird. Sadly, what passes for dissonance in most popular music (and not just today's) lies in confrontational lyrics, loud playing, and quirky performance styles. It is more of a performance and poetic phenomenon than a musical one.