What notes make up Bm7b5 on piano?

Spelled out, Bm7b5 is B, D, F, A — B plus the half-diminished 7th formula's other notes above it. In root position that's the order on the keyboard; inversions simply move a different note to the bottom of the stack.

Is it necessary to fit all 4 notes of Bm7b5 under one hand?

For most hands, yes — it fits in one hand. Still, plenty of players drop the root into the left hand and keep the right hand lighter, especially when the tempo picks up.

How would a theory teacher describe Bm7b5's function?

As the half-diminished viiø7 in C major, or the iiø7 chord that opens a minor-key ii–V–i — that's its default job. The flatted 5th removes the stable perfect fifth a minor 7th chord would otherwise have, so it almost always keeps moving toward a dominant chord next.

What's the closest related chord to Bm7b5?

Raise the flatted 5th back up a half step and Bm7b5 becomes a plain minor 7th chord — the lowered 5th is what pushes it from merely mellow into genuinely unstable.

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Bm7b5 Chord on Piano

Bm7b5 = B – D – F – A (Root, Minor 3rd, Tritone, Minor 7th)

Bm7b5 is built from B, D, F, A — root, and the rest of the half-diminished 7th formula stacked above it. Play Bm7b5 and the character is immediately moody, sitting between minor and diminished. On the keyboard B is the white key right after the three-black-key group, with no black key directly above it, and the chord itself is four notes that typically land under fingers 1, 2, 3, and 5, or 1, 2, 4, 5 if that fits better. It works as the half-diminished viiø7 in C major, or the iiø7 chord that opens a minor-key ii–V–i, and the flatted 5th removes the stable perfect fifth a minor 7th chord would otherwise have, so it almost always keeps moving toward a dominant chord next. Root included, that's 4 notes total — keep that figure in mind if a written voicing ever looks like it's missing one.

The harmonic role here is the half-diminished viiø7 in C major, or the iiø7 chord that opens a minor-key ii–V–i, which is the setting it shows up in most frequently. Because it fits easily under one hand, the bottleneck to playing it well isn't reach — it's repetition, so drill it alone before adding a moving bass line beneath it. D anchors first inversion once it's moved to the bass under the remaining notes — with a four-note shape, knowing the inversions isn't optional if you're reading real chord charts. You'll hear it worked into classical half-diminished passing chords regularly, and it recurs in minor-key jazz ii–V–i turnarounds too. The flatted 5th removes the stable perfect fifth a minor 7th chord would otherwise have, so it almost always keeps moving toward a dominant chord next. Because B is white key right after the three-black-key group, with no black key directly above it, the white key sits in the most natural reach for the hand, needing no forward adjustment at all. Given a bass line underneath, there's little reason for the left hand to play more than the root and 7th — the rest belongs to the right hand's color tones. This triad doesn't have a fixed home register — parked near middle C it comps normally, dropped low it reads as a bass punch, and lifted high it turns airy. Most players end up recognizing Bm7b5 by feel and by its moody, sitting between minor and diminished sound well before they can name every note in it from memory.

Voicings

Root Position

First Inversion

How to Practice It

Build Bm7b5 hands separately before combining them. Right hand: fingers 1-2-3-5 as a starting point — swap to 1-2-4-5 if your fourth finger feels stronger there across B, D, F, A. Left hand: the root alone, or root plus fifth, an octave or two below. Because the shape sits comfortably under one hand, resist the urge to skip root position and jump straight to inversions. Once each hand is confident alone, practice the chord in context: play the chord immediately before it, then land on Bm7b5, and listen for whether the transition sounds smooth or requires a visible jump. Repeat that two-chord move slowly, gradually increasing tempo only once the shape change is clean. It's easy to confuse this with a plain minor 7th at a glance; the flatted 5th is the one note that makes the whole chord function differently, so isolate and check it specifically.

Common Progressions

iiø7 – V7 – i: Bm7b5 opening a minor ii–V–i in A minor
viiø7 – I: Bm7b5 resolving up a half step into C major
Bm7b5 as a dark pre-dominant chord just before the V7 in a minor key

FAQ

What notes make up Bm7b5 on piano?: Spelled out, Bm7b5 is B, D, F, A — B plus the half-diminished 7th formula's other notes above it. In root position that's the order on the keyboard; inversions simply move a different note to the bottom of the stack.
Is it necessary to fit all 4 notes of Bm7b5 under one hand?: For most hands, yes — it fits in one hand. Still, plenty of players drop the root into the left hand and keep the right hand lighter, especially when the tempo picks up.
How would a theory teacher describe Bm7b5's function?: As the half-diminished viiø7 in C major, or the iiø7 chord that opens a minor-key ii–V–i — that's its default job. The flatted 5th removes the stable perfect fifth a minor 7th chord would otherwise have, so it almost always keeps moving toward a dominant chord next.
What's the closest related chord to Bm7b5?: Raise the flatted 5th back up a half step and Bm7b5 becomes a plain minor 7th chord — the lowered 5th is what pushes it from merely mellow into genuinely unstable.

Bm7b5 on other instruments: Bm7b5 on Guitar. Related: how chords are built, chord finder.