I’m not a banjo player. But I play guitar, and something I’m dabbling in is playing five-string banjo parts on guitar.
You tune the guitar to Open E (E-B-E-G#-B-E, low note to high note).
Then you capo at the third fret, moving it up to G-D-G-B-D-G.
Now, a five-string banjo is usually tuned to Open G. That’s D-G-B-D for the four long strings, with the short string tuned to G, one octave above the other G string.
So the fifth, fourth, third and second strings on your guitar are now tuned to the same notes as the four long strings on a banjo, in the same order.
And the first string on your guitar is tuned to the same note as the short string.*
You also have a low G note that isn’t on a banjo. I usually perform solo, and that bass note is useful to play rhythm guitar parts in between the banjo parts.
Performing solo, it can be a challenge to keep the music from sounding all the same. So it’s nice, and convenient, to throw in a banjo song for variety when I’m tuned to Open E.
I thought I’d discovered this, but it’s been around. There’s a really good guitarist in Sweden namd Martin Tallstrom who makes use of it. He plays a killer version of “Jesse James”.
*I would imagine that if you’ve played an actual banjo, it would take some effort to get used to playing short-string notes on the opposite side on the guitar.