Banjo Adim chord (Double C)A diminished on the 5-string banjo: 0 2 0 1, and 5 more shapes

Frets, string 4 to string 1: 0 2 0 1 (open position)

1. String 4 (C): open, C
2. String 3 (G): 2nd fret, middle finger, A
3. String 2 (C): open, C
4. String 1 (D): 1st fret, index finger, E♭
5. String 5, the short g: open, G, not in the chord

Sounds: C A C E♭  ·  Adim is A, C, E♭ (1 · ♭3 · ♭5)

Found in: C dorian (vi°), G minor (ii°), B♭ major (vii°), F mixolydian (iii°)

The 5th string: the short g adds the ♭7 over Adim, a colour rather than a clash.

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