C#min7#5

Construction

Built from these intervals: 1-b3-#5-b7.

The b3 establishes minor quality. The #5 raises the natural 5 by a half step, pulling the chord toward augmented territory without leaving minor behind. The b7 keeps it in the seventh-chord family. Min7#5 is min7 with the 5th raised a half step -- an alteration (a chord tone raised or lowered by a half step from its natural position) that destabilizes an otherwise familiar sound. The interval from b3 to #5 spans five half steps, enharmonically a perfect 4th though spelled as an augmented 3rd.

Harmonic Function

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

• Color chord -- used for its unique sonic character rather than traditional tonal function, placed wherever that instability serves the music.
• Chromatic passing -- often serves as a chromatic connector between more stable chords, its ambiguity smoothing transitions. For example, inserting min7#5 between i7 and iv7 creates a chromatic bridge.
• Modal chord -- does not occur naturally in major, harmonic minor, or melodic minor scales. It arises in certain modal and synthetic contexts, making it a deliberate color choice rather than a diatonic default.

Character

Ambiguous and unsettled. The #5 contradicts the b3's darkness with an upward brightness, leaving the chord suspended between minor and augmented identities. Compare to min7: min7 has a natural 5 where min7#5 has #5, and that single raised tone destabilizes the chord's center of gravity. Where min7 sits comfortably in any key, min7#5 belongs nowhere in particular -- which is exactly its value as a color chord for moments that need to sound unfamiliar.

Related Sounds

These chords share elements of the minor seventh structure -- each changes the 5th or 3rd:

• min7 (1-b3-5-b7) -- natural 5 instead of #5, stable and ubiquitous; the parent chord before the alteration
• min7b5 (1-b3-b5-b7) -- b5 instead of #5, half-diminished quality with clear function as ii in minor keys
• aug (1-3-#5) -- shares the #5 but has a natural 3, pure augmented symmetry
• 7#5 (1-3-#5-b7) -- dominant version with #5, the natural 3 creates a tritone (the interval of six half steps) with the b7 that min7#5 lacks

Voice Leading

Voice leading tracks how individual notes move from one chord to the next. The #5 pulls upward by a half step, making chromatic resolution the chord's most natural connection.

• min7#5 to bVImaj7: The #5, enharmonically the root of bVI, holds as a common tone. The b3 holds as the 5 of bVI. The b7 steps down to the root of bVI or holds. Three shared tones make this nearly seamless.
• min7#5 to iv (chromatic passing): The #5 steps down a half step to the b3 of iv. The root holds as the 5 of iv. The b7 holds as the 11 of iv. Chromatic passing motion into a minor iv.
• min7#5 to V7 (chromatic passing): The #5 steps up a half step to the 3 of V7. The b3 stays as the b7 of V7. The root holds as the 4 of V or resolves to the 3. The #5's upward pull lands on a strong chord tone of the dominant.

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

Practice Seeds

Spot the difference. Play min7, then min7#5 on the same root. The raised 5th is the only change -- hear how it destabilizes the familiar min7 sound and pushes the chord into unfamiliar territory.

Fifth spectrum. Play min7b5, min7, min7#5 in sequence on the same root. Hear the 5th move from b5 to natural 5 to #5 across three chords -- a full spectrum of how the 5th shapes a minor seventh chord.

Chromatic insertion. Place min7#5 between i7 and iv7 in a minor key. Listen for how its ambiguity smooths the transition -- the #5 acts as a chromatic passing tone between the natural 5 of i7 and the root of iv7.

Resolve the #5. Play min7#5, then let the #5 step up by half step to the root of the next chord. Train your ear to hear the #5 as a leading tone pulling upward -- this is the chord's most characteristic voice-leading move.