F#7

Construction

Built from these intervals: 1-3-5-b7.

The 3 brings brightness and establishes major quality. The 5 provides stability. The b7 -- two half steps below the octave -- pulls the chord toward resolution. Together the 3 and b7 form a tritone (the interval of six half steps), and that tritone is the engine of dominant function. This is the foundational dominant seventh chord, the template for every dominant extension and alteration.

Harmonic Function

In Roman numeral analysis (uppercase = major, lowercase = minor):

• V7 in major -- the primary dominant, resolves to I. The tritone between 3 and b7 resolves outward: the 3 rises to the root of I, the b7 falls to the 3 of I.
• V7 in minor -- resolves to i. Harmonic minor (the minor scale with a raised 7th degree) supplies the leading tone -- the note a half step below the tonic that pulls resolution home.
• I7 in blues -- dominant seventh as tonic. Classical harmony treats the tritone as tension that must resolve, but blues plants that tension on the tonic and lets it sit. The restlessness becomes the color, not the problem.
• Secondary dominant -- a technique where any chord in the key is approached by its own V7, creating chromatic pull. In a chain like V7/V resolving to V, each secondary dominant borrows the dominant's resolution power temporarily.

Character

Tense and forward-moving. The tritone between 3 and b7 creates restlessness that leans toward resolution -- this is why V7-I is the strongest cadence in tonal music. In blues, that restlessness sits on the tonic instead: the tension is not a problem to solve but the defining sound of the genre. Compare to min7: both share the b7, but dom7 has a natural 3 where min7 has b3. That natural 3 completes the tritone and demands resolution; min7, with no tritone, simply settles. Dom7 pairs with the Mixolydian scale (1-2-3-4-5-6-b7).

Related Sounds

These chords are closely related -- each modifies one interval:

• min7 (1-b3-5-b7) -- same b7 but no tritone; stable where dom7 is restless
• 9 (1-3-5-b7-9) -- adds brightness on top of the dominant tension
• 7sus4 (1-4-5-b7) -- a suspension where the 3 is replaced by 4, dissolving the tritone into open ambiguity
• 7b9 (1-3-5-b7-b9) -- darkened dominant, strong pull toward minor resolutions
• 7#9 (1-3-5-b7-#9) -- aggressive dominant with major-minor clash; pairs with the altered scale (seventh mode of melodic minor)

Voice Leading

Voice leading tracks how individual notes move from one chord to the next. The tritone resolves by contrary motion -- the 3 moves up while the b7 moves down -- and that outward pull is what makes dominant resolution feel inevitable.

• V7 to I: The 3 moves up a half step to the root of I. The b7 moves down a half step to the 3 of I. The tritone opens outward into the tonic.
• V7 to vi: Deceptive cadence. The 3 still moves up a half step to the b3 of vi, but the bass moves to the root of vi instead of I, surprising the ear while still releasing tension.
• V7 to i: The 3 moves up a half step to the root of i. The b7 moves down a half step to the b3 of i. The same tritone resolution works into minor, which is why harmonic minor exists.

These movements apply in any key -- the intervals are the same regardless of root.

Practice Seeds

Find the tritone. In any dom7, identify the 3 and b7 and play them together. That dissonant pair is the source of every dominant resolution -- hearing it in isolation builds awareness of what drives the chord.

Resolve it. Play V7 to I in several keys, listening for the 3 moving up and the b7 moving down. This builds functional hearing of the strongest cadence in tonal music.

Dom7 vs. min7. Play a dom7 and a min7 from the same root, back to back. The only difference is the 3 vs. b3 -- hear how that single interval creates or removes the tritone's pull.

Blues tonic. Play a 12-bar blues using I7, IV7, and V7. Notice how the dominant seventh functions as tonic on I, subdominant on IV, and dominant on V -- three different roles for the same chord type.