What purpose do chords serve in music?

Question

I'm a complete beginner to music theory and have recently been learning a few basics.

One thing I can't wrap my mind around are chords, and to a certain extent, chord progressions. I know how they are defined and how you play them - however I can't tell how one applies them to a piece of music.

In a similar sense that one can consider the bassline/melody/drums "separate pieces" of a piece of music, can you think of chords and chord progressions as their own "building block" of what makes a song? Or are chords and chord progressions simply "part" of these mentioned "pieces", with some melodies having an occasional chord playing within them? Basically viewing chords as "special tones" you can play when you feel like it - another part of your tonal palette.

For example, I've been listening to one of my favorite tracks as of late and it sounds like the bassline consists of nothing but a very low sounding chord progression. Yet in another track, it seems as if the chord progression was just another "building piece" of the song, accompanying the melody in its own, more separate fashion.

Answer 1

Basically what you're asking is "what is tonality." And the first disclaimer is that hasn't always been "a thing" in Western music, and isn't always in other music-cultures. Just as a "bassline/melody/drums" construct doesn't make sense for Gregorian chant,* neither do "chords" or "chord progressions."

First of all, I used the word "tonality." Let me unpack that; it includes the idea of "being in a key," and the idea that that key uses certain chords, and uses them in certain ways. It's more than a tool in your toolkit; it is the toolkit, the workshop in which you use it, and the way we understand the concept of "tool." It's the way we've "done business" in music from somewhere around the late Renaissance all the way through Justin Bieber. You can point to individual exception songs, or to entire branches that revolt against the idea of being "in a key" (atonalism), but it's so ingrained that the only way to exit the construct is by explicit choice.

Analyzing the music by contrasting "bassline, melody, and drums" is a useful approach, but it breaks the music into different roles. By analogy, language can be broken into nouns, verbs, and adjectives... but the thing that matches "tonality" in that example is "grammar." It's the assumptions and conventions about how you use your musical tools, and the way we're used to making sense of what we hear.

Now, you used the word "chords." That could mean "stacks of 3 or more notes that play simultaneously," or it could refer to the imaginary or implied chords that are suggested even if not actually heard. If I sing "Happy Birthday to you," with only myself singing, then you're not hearing chords as in stacks of notes; that would take at least three voices. But the melody suggests (and we're all used to) a "V chord" on the first "you," a "I" on the next "you," and finally a IV, V, and I at the end of the song, just like millions of symphonies, sonatas, doowop songs, rock ballads, and techno drops. If you're listening to your favorite track and hear the bass changing notes, chances are those notes are implying full chords and their tonal functions, just as the 7 bass notes here....

... contain the seeds for the chords that arrive by 1:18.

At the same time, I could imagine a work in which bass and melody weren't related by a tonal relationship, but developed their own patterns independently. (It might sound rather edgy, though, like this 1673 depiction of a lot of people singing different tunes at once:

* (Insert red herring about unspecified instrumental forces in medieval genres, ultimately getting into Hildegard von Bingen and devolving into critiquing various recordings.)

Answer 2

To understand chords, I find some history helpful.

Pre-chord history

The earliest Western music we know about is chant. ("Earliest" in this case meaning the first music where we can "connect the dots" to modern music.) In its simplest form, chant is one person singing one pitch at a time: melody, but only melody.

Eventually, musicians discovered that one could create a very compelling musical effect by accompanying a melody with a drone, a single sustained pitch. In the loosest sense, this is the "invention" of chords: more than one simultaneous sound, or put another way, more than one simultaneous voice.

From there, an evolution occurred in which a second drone was added, and then a second voice which moved in parallel with the melody.

This general practice — of having one or more drone or parallel voices — is called organum (Wikipedia: Organum).

The history described here is illustrated in the video "Early Organum" by David Goodall.

The "invention" of chords

Eventually, musicians began to make these various voices truly independent of each other. That is, rather than singing a single pitch, or a melody that moved in lock step with another, it was more like two people each singing a different song, but where those two songs blended together in a pleasing way.

One of the masters of this was the composer Palestrina (Wikipedia: Palestrina), whose music was considered the model for the next century or so. One of his most important works was his Pope Marcellus Mass, which can be heard here, performed by the Tallis Scholars.

Composers and theorists began to study these independent voices to understand how certain simultaneous notes moved most effectively to another set of simultaneous notes. This, essentially, is the "invention" of chords: a theoretical construct to describe how one set of pitches moved to another set of pitches (a "chord progression"). The composer/theorist most credited with our modern way of thinking about chords, is Jean-Philippe Rameau (Wikipedia: Rameau.

Chords as musical tools

As composers shifted from considering independent melodies to thinking in terms of the movement of chords, chords took on a life of their own. They are both a set of notes played simultaneously, but also a descriptive tool for describing the sound of a piece of music.

Especially in jazz and popular music, songs are often written as a melody with a set of chord changes describing the overall sound desired. It's then up to the various musicians to "realize" those sounds, those chords.

In Classical music, chords are more "built in", in that the composer indicates more precisely what should be played and when.

Answer 3

In the broadest sense chords and other musical elements serve one main purpose: to express thoughts and feelings. Talking about "purpose" in art is a tricky business. If you try to stay objective about it, you can talk about stability/instability and consonance/dissonance as the dynamic forces in chords and harmony. Those elements give music a basic emotional sense of tension and release and sense of forward direction to start, continue, or stop.

When you mention that parts like melody and bass can seem like independent elements or work together, and ask whether chords can be treated like independent and singular elements, you get into the technical concept of musical texture.

When parts seem to be independent but work together that is usually called polyphony. Depending on the style of composition such independent parts can be constructed so that the combined parts make chords. That's a common way of describing harmony: multiple voices moving independently, the combination of parts at different points in time form chords, the flow of chords is the art of harmony. When each of those parts is a finely developed melody - like in a fugue by Bach - specific composition methods are used with the techniques of counterpoint.

But, chords can be treated in a more "generic" way in regard to the combination of parts. ("Block chords" is one way to describe what I mean by generic.) In that generic treatment chords do indeed become like singular elements as you suggested in your question. When chords are treated that way and combined with a single melody it is called homophony. A huge amount of pop music is homophonic: melody and chords with bass.

As you might expect there is a spectrum of styles between polyphony and homophony. It is not black and white, one or the other. In the long history of "classical" music polyphonic music tends to have a continuous rhythmic flow while homophonic music allows for more boldly demarked rhythms. That is a huge generalization, but it gives a general sense of why a composer might choose a polyphonic form over a homophonic form.