B diminished major 7th chord on bass (BdimMaj7)

Why it sounds like that

B diminished major 7th is built from the formula 1, ♭3, ♭5, 7. The diminished 5th between B and F creates a tritone that gives the chord its dark color. The major 7th A♯ is a leading tone that resolves upward to B. Compare with B minor 7th flat 5th, which has A instead of A♯.

What goes wrong with B diminished major 7th?

• Letting the ring finger flatten onto the 2nd string, which deadens the D.
• Pressing the index finger too hard, causing the 4th string to buzz against the fret.
• Allowing the pinky to drift sharp, making the 2nd string note sound out of tune.

When to use it

B diminished major 7th works as a passing chord in B minor, often between B minor and B minor 7th. Its tense sound suits jazz ballads and dramatic film cues. Use it to add chromatic motion on the bass.

Changing to and from B diminished major 7th

• Sliding the shape down two frets to the 5th fret gives A diminished major 7th.
• Sliding the shape up one fret to the 8th fret gives C diminished major 7th.

Which voicing to use

The 7th-fret position places the root B on the 4th string, giving a solid low foundation. The BdimM7/F inversion at the 1st fret puts F in the bass, creating a different color while keeping the same notes.