Banjo B♭m chord (Double C)B♭ minor on the 5-string banjo: 1 3 1 3, and 3 more shapes

Frets, string 4 to string 1: 1 3 1 3 (first position)

1. String 4 (C): 1st fret, index finger (barre), D♭
2. String 3 (G): 3rd fret, ring finger, B♭
3. String 2 (C): 1st fret, index finger (barre), D♭
4. String 1 (D): 3rd fret, little finger, F
5. String 5, the short g: open, G, not in the chord

Sounds: D♭ B♭ D♭ F  ·  B♭m is B♭, D♭, F (1 · ♭3 · 5)

Found in: F♯ major (iii), D♭ major (vi), A♭ major (ii), E♭ mixolydian (v), D♭ mixolydian (vi), A♭ mixolydian (ii)

The 5th string: the short g adds the 6th over B♭m, a colour rather than a clash.

Double C tuning: gCGCD, the short 5th string first, then strings 4 to 1.