The G/B chord is a slash chord or slashed chord, also called a compound chord. A slash chord is a chord whose bass note or inversion is indicated by the addition of a slash and the letter of the bass after the root note letter. It does not indicate “or”.
So, in other words: slash chords are just normal chords with one note changed. The note altered is the root note of the chord. The root note will be the lowest note of the chord, so we are simply altering (or changing) the lowest note of the chord.
The first chord (the chord on the left of the slash) is the main chord. The chord on the right of the slash is not a chord at all. It’s the name of the note that we want the lowest note of the chord to be.
With the G/B chord, the main chord form is that of a G chord, but instead of playing the normal 3rd fret of the E string root, we’ll use the B note on the 2nd fret of the A string as our root instead.
Using The G/B Chord
The G/B chord is most commonly used in the key of C as a connecting chord between the C and Am chords.
For example, try these chord progression:
C, G/B, Am
Am, G/B, C