Module 22 mini-test

1. What is chord substitution?

2. Why can D♭7 substitute for G7 when resolving to C?

3. What are the guide tones of G7?

4. What are the guide tones of D♭7?

5. What is the tritone substitute for D7?

6. What is the tritone-substituted ii–V–I in C?

7. What is a backdoor dominant into C?

8. What is the backdoor ii–V into C?

9. Why can common-tone substitutions work even when roots are remote?

10. Does “substitute” mean two chords sound identical?

Answers

1. Replacing a chord with another that can preserve enough of its function, voice leading, or melody relationship to work in the same location.
2. They contain the same dominant guide-tone tritone enharmonically.
3. B and F
4. F and C♭, with C♭ sounding as B.
5. A♭7
6. Dm7 → D♭7 → Cmaj7
7. B♭7 → C
8. Fm7 → B♭7 → C
9. Shared melody/inner notes plus smooth semitone voice leading can create strong continuity despite unrelated roots.
10. No. It means they can perform sufficiently similar harmonic work while producing different color.

The central idea of Module 22 is:

A chord's root is not the only thing that determines what it can do. Its guide tones, melody relationship, and voice leading can be even more important.

And now a progression that once looked impossible:

Dm7 → D♭7 → Cmaj7

should make sense: the bass moves D → D♭ → C, while the essential dominant voices still resolve B → C and F → E.

Module 23 will be much more pianistic: intros, fills, turnarounds, transitions, and endings—how to start a song without simply counting in, what to play when the melody leaves space, and how to finish with something more intentional than just hitting the tonic chord.