C#m7b5 is a half-diminished 7th chord, and on the bass it is played from the notes C#, E, G, B. On bass it is outlined with the arpeggio C#, G, C#, E — root, 5th, root, 3rd. This page is a complete reference for it: notes and intervals, fingerings, mistakes to avoid, the keys it belongs to and a short practice routine.
What notes are in the C#m7b5 chord?
The C#m7b5 chord is a half-diminished 7th chord, and its notes are fixed: C#, E, G, B. Every voicing on every instrument uses these same notes, in some order and in some octave — change one of them and you are playing a different chord. The table below lists each note with its interval from the root C#, so you can see the structure of C#m7b5 at a glance. On the bass, C#m7b5 is the arpeggio C#, G, C#, E — root, 5th, root, 3rd — and that order is the shape to learn.
| Note | Interval |
|---|---|
| C# | Root |
| E | b3 |
| G | b5 |
| B | b7 |
The root is C#, the note the chord is named after and the note your ear hears as home. Above it, the intervals in C#m7b5 are b3, b5, b7. Those intervals are the fingerprint of the half-diminished 7th quality — any chord with the same interval pattern, on any root, is the same kind of chord. On the bass, the notes appear in the order the fingering dictates, but the set of notes never changes.
C#m7b5 sounds dark, jazzy and unresolved — the half-diminished chord is the sound of the ii chord in minor keys. That character comes straight from the intervals above, not from the instrument: the same notes on piano, guitar or ukulele carry the same colour, even though the voicing changes. On the bass, the arpeggio C#, G, C#, E outlines C#m7b5 one note at a time.
Comparing C#m7b5 with its closest relatives helps to fix it in your ear. In short, half-diminished against diminished 7th: C#m7b5 keeps the flattened 7th B; the diminished 7th flattens it further to A#. The half-diminished sounds softer and more usable. Play both chords slowly, one after the other, and notice which note moves. Naming that note out loud while you play is the fastest way to learn the difference. On the bass, the arpeggio C#, G, C#, E outlines C#m7b5 one note at a time.
How to play C#m7b5 on bass
On the bass, C#m7b5 is not played as a full chord shape the way it is on guitar or piano. Instead you outline it with an arpeggio: the notes C#, G, C#, E, which are the chord tones of C#m7b5 in the order root, 5th, root, 3rd. That pattern is the working shape for this chord on bass, and it tells the listener exactly which chord is sounding, even though you never play all the notes at once.
Practise the arpeggio of C#m7b5 by playing C# on beat one, G on beat two, C# on beat three and E on beat four, one note per beat, letting each note ring for its full value. Then play it backwards — E, C#, G, C# — so your fingers learn the shape in both directions. The root C# is the anchor: it is the note the rest of the band listens for, so land on it cleanly and on time, and let the 5th G and the 3rd E colour the bar without pulling attention away from the root.
Once the straight arpeggio of C#m7b5 is comfortable, try playing just the root C# and the 5th G for a whole bar, then add the 3rd E on the last beat as a passing colour. That root-and-5th skeleton is how most bass lines outline C#m7b5 in a real song, and the full arpeggio is the version you use when the arrangement has space for it. Check the notes with the Bass Chord Finder and the Chord Finder, and practise the arpeggio against a slow metronome so the notes land exactly on the beat.
Common mistakes
These are the mistakes that most often make C#m7b5 sound wrong on the bass, and each one has a concrete fix. Work through them one at a time rather than trying to fix everything at once.
Playing the diminished 7th. The 7th here is B, not A#. Flatten it once more and you have the fully diminished chord. On the bass, play C#, G, C#, E and hear how the arpeggio spells out C#m7b5 without ever playing it as a block.
Using it as a tonic. C#m7b5 is a ii chord, not a home chord. It wants to move to the dominant and then resolve. On the bass, play C#, G, C#, E and hear how the arpeggio spells out C#m7b5 without ever playing it as a block.
Burying the flattened 5th. G is the note that defines this chord. If it is muted, the chord collapses into a minor 7th. On the bass, C#m7b5 is the arpeggio C#, G, C#, E — root, 5th, root, 3rd — and that order is the shape to learn.
Playing the arpeggio as a chord. Strumming all the notes of C#m7b5 at once on bass sounds muddy and hides the root. Play the arpeggio one note at a time, let each note ring, and keep the root C# as the note the listener hears first. On the bass, play C#, G, C#, E and hear how the arpeggio spells out C#m7b5 without ever playing it as a block.
Where C#m7b5 is used
C#m7b5 is not a diatonic triad in any major or minor key, because it is an extended or altered chord, but its base triad belongs to the key of E major, the key of A major, the key of B major. the ii chord in minor keys — the starting point of the minor ii–V–i. As a dominant-type chord it also points toward F# major, the key a perfect fourth above C#, which is the tonic it most often resolves to. That is where C#m7b5 does its work: not as a home chord, but as a chord that creates movement and then resolves. On the bass, the arpeggio C#, G, C#, E outlines C#m7b5 one note at a time.
Because C#m7b5 is an extended or altered chord, it appears in progressions as a colour or a dominant rather than as a diatonic staple. Try it in place of the plain C# triad in a progression you already know, and listen to how the extra notes change the feel — that substitution is the usual way extended chords enter real music. The Chord Progression Builder lets you try C#m7b5 in a progression in any key and hear how it connects to the chords around it. On the bass, play C#, G, C#, E and hear how the arpeggio spells out C#m7b5 without ever playing it as a block.
The same chord on other instruments is covered in C#m7b5 on guitar, C#m7b5 on piano, C#m7b5 on ukulele, and the scales that fit over it are the C# major scale and the C# minor pentatonic scale. Learning C#m7b5 on the bass and then checking it on another instrument is one of the best ways to fix the notes — C#, E, G, B — in your memory, because the notes stay the same while everything else changes.
Practising C#m7b5
A short worked example makes C#m7b5 concrete. Play the four-chord progression F# – C# – D#m – B in F# major, the key C#m7b5 most often resolves toward: F# – C# – D#m – B. Play each chord for one bar at a slow tempo, and listen to how C#m7b5 sounds in that sequence — whether it feels like home, like a lift, or like a chord on its way somewhere else. Then play the same four chords in a different order, starting on C#m7b5 itself, and notice how its character changes when it opens the progression instead of sitting inside it. On the bass, play C#, G, C#, E and hear how the arpeggio spells out C#m7b5 without ever playing it as a block.
For a second exercise, play C#m7b5 and then the chord a fourth above C#, back and forth, four times each. That move — a chord and the chord a fourth above it — is the most common resolution in Western music, and it is the move C#m7b5 is built for when it acts as a dominant. Finish by playing C#m7b5 on its own, slowly, and naming each note out loud as you play it: C#, E, G, B. Naming the notes while you play them is what turns a shape into knowledge you can use in any key. Test yourself with the Practice Chord Quiz and keep time with the Metronome as the tempo rises. On the bass, play C#, G, C#, E and hear how the arpeggio spells out C#m7b5 without ever playing it as a block.
Frequently asked questions
Should you play the full C#m7b5 chord on bass?
Usually not. On bass the chord is outlined with the arpeggio C#, G, C#, E, not strummed as a block. Playing all the notes at once sounds muddy in the low register and hides the root, which is the note the rest of the band is listening for.
What does m7b5 mean in C#m7b5?
It means a minor 7th chord with a flattened 5th: C#, E, G, B. The triad is diminished (C#, E, G) and the 7th is flattened (B), hence half-diminished. On the bass, the arpeggio above shows where that note sits.
Where is C#m7b5 used?
As the ii chord in minor keys, in the minor ii–V–i progression, and in jazz standards and bossa nova. It almost always leads to a dominant chord. On the bass, the arpeggio above shows where that note sits.
What is the difference between C#m7b5 and C#dim7?
C#m7b5 has the flattened 7th B; C#dim7 has the double-flattened 7th A#. C#m7b5 sounds softer and more usable; the diminished 7th sounds tenser and more dramatic. On the bass, the arpeggio above shows where that note sits.
How do you play C#m7b5 on the bass?
Outline it with the arpeggio C#, G, C#, E: root, 5th, root, 3rd. Play one note per beat, with the root C# on beat one, and let each note ring. That arpeggio tells the listener exactly which chord is sounding, even though you never play all the notes of C#m7b5 at once.