Can someone please explain how chords work within a song? My previous post was on chord progressions and how to hear and listen for them in a song. More people than Not have told me to listen intervallic structure in the bass line. I have no problem hearing and figure out the bass line but how does this relate to the chord changes of a song? Furthermore, I didn't know chords could be split amongst instruments (voices). Please explain these concepts and theories to me.
Yep, the instruments and voices all conspire together to make up the harmony. In a typical rock band the rhythm guitar player is usually playing the chords. But in other cases, no single instrument plays chords.
For example, in an a capella vocal arrangement, no one person sings more than one note at a time. But there are still chords. Writing such arrangements is a bit like making a crossword puzzle--each line has to satisfy two constraints: looking at the music vertically (fixing one moment in time), it has to be part of a chord; looking at the music horizontally (following one voice), it has to make a nice melody.
The vertical constraint isn't quite so rigid, actually, as individual parts often use non-chord tones, as a way to get from one place to another, or as a way to create some tension.
But as a general rule, the lower in pitch you go, the less freedom you have to do that sort of thing, because non-chord tones at the bottom tend to sound muddier.
And the bass line in particular tends to stay very close to chord tones and even, wherever possible, to the root of each chord.
This is especially true on the strong beats: in 4/4 time, beat 1 of each measure is the strongest beat, beat 3 the next strongest. When bass lines do use non-root or non-chord tones, they often fall on weaker beats, and are often used as passing tones along the way to the root of the next chord.
So that's why the bass line is a good place to start figuring out harmony: if the bass plays a G on the first note of a measure, chances are very good the chord is actually a G chord. Or if not a G, at least a chord with a G in it.