Fdim is a diminished, spelled F, Ab and Cb. In Open G tuning (D2 G2 D3 G3 B3 D4) the easiest shape is 313103, which sits at fret 1, needs a barre across 3 strings at fret 1 and lets 1 string ring open. 12 positions for it are shown below, from the nut up to fret 13.
Notes and intervals
Note
F
Ab
Cb
Interval
1P
3m
5d
12 ways to play it
Ordered by how hard they are to fret, easiest first, one per position on the neck. Fret numbers are relative to the position marked beside each grid.
313103sits at fret 1, needs a barre across 3 strings at fret 1 and lets 1 string ring open343406sits at fret 3, needs a barre across 3 strings at fret 3 and lets 1 string ring openx1091099sits at fret 9, needs a barre across 4 strings at fret 9 and mutes 1 stringx46466sits at fret 4, needs a barre across 3 strings at fret 4 and mutes 1 string15131513015sits at fret 13, needs a barre across 3 strings at fret 13 and lets 1 string ring openx1061009sits at fret 6, spans 4 frets, lets 1 string ring open and mutes 1 stringxx15131215sits at fret 12, spans 3 frets and mutes 2 strings31310xsits at fret 1, needs a barre across 3 strings at fret 1, lets 1 string ring open and mutes 1 stringxx3103sits at fret 1, spans 2 frets, lets 1 string ring open and mutes 2 stringsxx310xsits at fret 1, spans 2 frets, lets 1 string ring open and mutes 3 strings31340xsits at fret 1, spans 3 frets, lets 1 string ring open and mutes 1 string34310xsits at fret 1, spans 3 frets, lets 1 string ring open and mutes 1 string
Keys Fdim belongs to
Fdim is diatonic to 8 of the 96 keys this app knows, playing a different role in each.