How does one know whether a straight, sixth, seventh, diminished, or augmented chord needs to be played?

Question

I'm sure this fairly stupid question comes up periodically.

Still, here's the verse from "Puttin' on the Ritz":

F Abdim7 Gm7 C7
Have you seen the well to do?
F Abdim7 Gm7 C7
Up and down Park Avenue?
Ab Bdim7 Bbm7 Eb7
On that famous thoroughfare?
Ab Bdim7 Bbm7 Eb7
With their noses in the air?
C C#dim7 Dm7 G7
High hats and arrowed collars
C C#dim7 Dm7 G7
White spats and fifteen dollars
Am D7
Spending every dime
G7 C7 Caug
For a wonderful time!

There are sevenths, diminished chords, and augmented chords. The song is played in F, which means (for instance) that C# is not even part of the scale, and yet the music seems to call for a diminished C# 7 - how? why?

I mean, yes, try them all out and see which one sounds best, I get that.

But is there a general rule of some sort?

Answer 1

It is a little difficult to answer your question without knowing your understanding of theory. C'est la vie. I will do my best.

The first progression is fairly common: F, A♭ dim7, G min7, C7. F is the tonic (I) chord, the G min7 is the II chord, and the C7 is the dominant (V) chord. The function of a dominant chord is to lead you back to tonic. In jazz, the II chord is a chord that leads you to the dominant chord to provide harmonic interest preceding the V chord. In this progression, there is a Ab dim7 before the II. This occurred frequently in earlier jazz to add chromaticism to the progression. Non technically, it sounds bluesy.

The second progression is a transposition of the first.

In regard to seventh chords, jazz almost always uses seventh chords or other added note chords. Most chords with a '7' are constructed with a minor seventh above the root of the chord. The only exception is a FULLY diminished seventh chord, which has a diminished seventh (enharmonic with a major sixth) above the root. If there is a major seventh above the root, the chord symbol will indicate that (G maj7 or [less frequently with minor chords] A min maj7).

In the third progression, C, C♯ dim7, D min7, G7, the C♯ dim7 chord, being a half step below the D min, is leading you to the D min7 chord, and is a substitute for a dominant chord of the D min (very common in baroque music as well). You might get a clearer answer by (if you have not done these things already) studying a general music theory book, studying jazz theory specifically, and playing many jazz tunes. Aebersold play alongs are great sources for jazz tunes. Bon chance!

Answer 2

... and yet the music seems to call for a diminished C# 7 - how? why?

I can answer to you how and why:

Actually we have here only one progression in which the diminished chord is easily fitting:

It is the famous I-VI-II-V. (first in F, then in Ab and in C.

Depending of the melody VI and II can be minor or major chords. As major chords they are secondary dominants. In some tunes they can be both used.

Now the diminished chords are just substitutions for the VI and secondary dim. seventh of the predominant VIIdim7/IIm.

e.g. in C major key:

a,c,e,g respectively a,c#,e,g can be replaced by eb,gb,a,c or c#,e,g,bb

How does one know ...

a) by knowing the theory and functions as explained above

b) by listening and analyzing what you here

c) and if there is no fixed progression or version that you will play along then it‘s up to you and you can decide whether you will bring more colors in your accompaniment

try it out!