Is the IV Chord a New Tonic? Navigating the I to IV Change
What was the question?
David asked about the movement from C Major (I) to F Major 7 (IV). Specifically, he wondered if the target chord (F) should be treated as a non-tonic sound because the guide tones resolve there, or if the upper structure (Am7 over F) makes it feel like a tonic. Later, Joel clarified if playing a Bb note in this transition implies a secondary dominant.
(01:31 / 14:13)
The core idea (in plain English)
When you move from the I chord to the IV chord, the IV chord often sounds stable, almost like a temporary home base (tonic). Technically, the upper structure of F Major 7 is A Minor 7, which functions as a tonic sound in the key of C. To make the movement stronger and clearer, we often turn the I chord into a secondary dominant (C7) by introducing the flat 7 (Bb) right before the change. This forces the ear to accept the F chord as the new "one" for a moment.
(04:21)
Fretboard breakdown (what to play)
Identify the Upper Structure: Recognize that valid extensions for F Major 7 create an A Minor 7 shape. This connects the IV chord back to the tonic family. (04:21)
Use the Secondary Dominant: Instead of just playing C Major to F Major, visualize C7 going to F. (06:13)
Target the Third: Aim for the third of the new chord. If you interpret the F chord as a temporary new "one," you can approach its third using a secondary dominant line. (08:05)
The Bb Passing Note: As Joel noted, playing the Bb (the flat 7 of C) over the C chord creates that C7 sound, which pulls strongly to the A (the third of F). (14:13)
Common mistake to avoid
A common mistake is treating the IV chord strictly as a "subdominant" tension without acknowledging its stability. Be careful not to play lines that sound unresolved when you land on the IV chord. If it acts as a temporary tonic, your lines should resolve to stable chord tones like the third or major seventh.
A 10-minute practice assignment
Take a simple I to IV progression (e.g., Cmaj7 to Fmaj7).
Play the Cmaj7 shell voicing.
Before changing chords, alter the Cmaj7 to a C7 (add the Bb).
Resolve the Bb down a half step to A (the third of Fmaj7).
Repeat this in three different positions on the neck to map the voice leading.
(14:40)
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