Again, the following discussion assumes the G tuning.
In a previous post, “An Easy A,” I discussed the advantage of fretting the 5th string when you want to “sweeten” a chord that would otherwise be dissonant. It’s a help in playing the two keys the banjo works best for: G and C.
Similarly, fretting the 5th string can help the two best minor keys. In G minor you can sweeten the D7 chord; in C minor you can sweeten the F minor chord.
Unlike those 2 majors and 2 minors, there are keys that banjo players use less. They all have one thing in common: for each of them the G 5th string clashes with the tonic chord (the one the key is named for). It may be OK to clash with other chords, but not the tonic.*
The capo-ble banjo gives a new slant to this, because the 5th string can be fretted to avoid the clash. Notably, the capo-ble banjo makes D minor one of the best minors: Fretting the 5th string to A makes a sweet D minor chord possible; the other two most important chords have G as a component.
The arrangement of “Scarborough Fair,” by my teacher, Joe Hetko, shows how that works. You can see it in the excerpt above, and see and hear it in TEFView. Click the following link, select “cb Scarborough Fair,” download, play in TEFView.
*Sometimes advanced players switch to another key and clash away for awhile, before returning to the original key.