A capo is a clamp placed across all strings at one fret. It works like a moved nut: everything sounds higher, but you play the same chord shapes as before. That’s especially handy on banjo, since so much is played in G – with a capo you can use the same shapes in A or D.
What is it for?
- A song suits your voice – or your class’s voices – better.
- Other instruments are playing in A, but you only know the shapes in G.
- You want to play a tune exactly as you learned it from tab, just in another key.
Which fret gives which key?
Each fret raises everything by a semitone. You play shapes in G:
- Capo at the 2nd fret → sounds in A
- Capo at the 3rd fret → sounds in Bb
- Capo at the 4th fret → sounds in B
- Capo at the 7th fret → sounds in D
The fifth-string question
The short fifth string only starts at the 5th fret, so the capo can’t reach it. It has to be raised by the same number of semitones as the other strings. With the capo at fret 2, it should play a instead of g. There are two ways to do that:
- Tune it up: simply raise string 5 by two semitones. Quick and easy – just turn carefully so the string doesn’t snap, and tune it back down afterwards.
- Small spikes on the neck: many banjos have little hooks or spikes (often called “railroad spikes”) beside string 5, typically at frets 7, 9 and 10. You tuck the string under one, and it acts like a capo for that string. For a capo at fret 2, use the spike at fret 7.
How keys relate to each other, and how to change key without a capo, is explained in transposing.