6 String Freedom

Part 8: Add the seventh, one ingredient at a time · Lesson 071 / 117

Dominant seventh: major third, minor seventh

Today’s one thing

Build C7 and distinguish it clearly from Cmaj7.

C7 contains C, E, G and Bb. Its formula is 1–3–5–b7: a major triad plus a minor seventh. This chord quality is called dominant seventh.

Compare Cmaj7 = C–E–G–B with C7 = C–E–G–Bb. Only the seventh changes in this comparison. Compare Cm7 = C–Eb–G–Bb with C7 and only the third changes. Inspect one comparison at a time.

A familiar C7 grip is x32310: C–E–Bb–C–E. It omits the fifth G and repeats other chord tones. An omitted fifth can still leave the characteristic root, third and seventh clear. We will explore such practical voicings later.

For now, “dominant seventh” names the interval structure. It does not by itself prove how the chord functions in a piece. That distinction matters particularly when blues arrives near the end of the course.

Hear it

Seventh Qualities

Audio file

Four-beat count-in · 60 BPM · Warm sampled electric guitar. Listen once before playing along.

A concrete example

Cmaj7: C E G B. C7: C E G Bb. Cm7: C Eb G Bb. Compare the seventh first, then the third.

C chordCEADGBe×C7 chordC7EADGBe×
Low E is left; high E is right. Open circles mean open strings; × means leave the string silent. Use relaxed, comfortable voicings.

Fretboard view

High E (string 1) is the top line, matching guitar tablature. Select a note to hear it.

Root / tonicChord toneTargetChanged / colour noteOther note
G7: G–B–D–F
Open G7 (320001), showing the lowered seventh F.
Guitar fretboard diagram: G7: G–B–D–F. High E string on top, frets 0 to 3. Notes G, B, D, G, B, F.
G7 is a dominant-seventh quality; compare its F with the F♯ of Gmaj7.
Play notes from a larger button list

One small map at a time. Hear the notes, then play the example without looking.

Try it, slowly

  1. Build C7 as a four-note arpeggio.
  2. Lower B to Bb in a Cmaj7 comparison.
  3. Inspect x32310 and identify which theoretical chord tone is absent.

Check one idea

Are C7 and Cmaj7 interchangeable names?

Show the explanation

No. C7 includes Bb, a minor seventh; Cmaj7 includes B, a major seventh. Their sound and harmonic use can differ.

A good place to stop

You can distinguish the three seventh-chord formulas through their third and seventh.

Return to the example after a short break. A clear explanation matters more than speed.