To play the Fdim chord, place the middle finger on the 4th fret of the top g-string, little finger on the 5th fret of the C-string, ring finger on the 4th fret of the E-string, and index finger on the 2nd fret of the bottom A-string.
The Fdim chord contains the notes F-Ab-Cb.
To build an Fdim chord, take the diminished triad formula (1-b3-b5) and apply it to the F major scale (F, G, A, Bb, C, D, E).
Identify the first, third, and fifth scale degrees in an F major scale which are F-A-C.
Lower the third and fifth scale degrees a half step in accordance with the diminished triad formula, which results in the notes F-A-Cb for the Fdim chord. In this case, the "Cb" is the enharmonic equivalent of the note B.
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