Isn’t the root progression or chord progression of a song meant to anchor in a foundation for rest of the instruments to experiment over?

Question

What I mean is, isn’t the idea of creating and using a root progression or chord progression for it to be the foundation for a composition. With pop music (rap, r&b, latin, pop rock, country) the progressions are typically very simple switching between maybe two to four different progressions per song. Classical on the other hand, the progressions may switch a lot more.

But anyways, isn’t the typical idea to use an accompanying instrument to set the foundation for the composition so the singer, lead guitarist, etc can noodle over it and create their different parts while staying in key and in rhythm. Especially with a solo singer for example, playing chords on a guitar or keyboard and experimenting with different melodies until writing something you like.

And lastly, what I mean with root progressions or chord progressions is aren’t they practically the same thing, because, if you have a 4 chord progression, say Am C E G, wouldn’t playing just A C E G and not the full chord still do the same job as setting a foundation? As if it were something like two voice counterpoint, or figured bass.

When I listen to music, I can always hear the progression of the roots, as if the roots are the anchor and the rest of the voices, including the rest of the notes in the chords, are simply an extension of the root notes. And it makes me think of the harmonic series, because if the current root note that is ringing out is on a C whatever other notes are being played will be most in tune based on the harmonic series (C, C, G, F, E). And thats the C sus 4 chord or C major.

There is an excerpt from the book Jazz Composition and Orchestration by William Russo. He says:

“Why is it so important to know the root of the chord? Because the roots of the chords will sound whether we want them to or not, whether or not the alphabetical symbol is correct. The root progression which emerges may not coincide with what we think we have written; it may be better or it may be worse; but art does not permit chance. The root progression supports the work. The total root progression is heard as a substantive element, almost like another melody, and it determines the tonal basis of the music. And the tonal basis of a piece is very important to the construction of themes and to the orchestration.”

Answer 1

You posted a lot of statements rather than questions. Here is one comment and one answer:

Classical on the other hand, the progressions may switch a lot more.

Some. But, a lot doesn't use much beyond I, ii, IV, V and vi along with transposition.

...root progressions or chord progressions is aren’t they practically the same thing..?

Mostly the same. But if you really indicate roots only it will leave out possible sevenths or other chord extensions, inversions, and possible mode mixing.

Think of a songs like Life on Mars or My Funny Valentine where the roots alone will miss the very, very important descending bass lines.

The important thing is to understand the difference between chord roots and a bass line/part. They aren't necessarily the same thing. And as a bass part becomes more melodic it tends to get away from playing just chord roots.

Answer 2

Yes, if you had to use just one thing as the harmonic foundation, it would probably be the bass line. But just C in the bass doesn't tell us whether it's C major or C minor (or C7, Cm7, Cm7b5, C9(#11), D/C... etc. etc.)

I'm not sure what your actual question is, though? Everything you say is true, in its way. None of it is the Answer To Everything.

And there's a heck of a lot of music which ISN'T about improvisation. A lot is meticulously composed and notated, and our job is to play it as accurately and beautifully as possible, not to mess with the notes!