Banjo players have the option of attaching a capo to a banjo's neck to raise the pitch of the banjo strings. This is a convenient way to change from one key to another without changing left-hand fingerings. A capo is only effective if you know how to attach it to a banjo properly. If you play a five-string banjo, you must also find a way to adjust the tuning of the fifth string, since banjo capos only reach across four strings of the banjo.
Choose a capo. There are a number of capo styles, including elastic capos, clamp capos and thumbscrew capos. Each style of capo holds a bar against the banjo strings using a strong elastic band, clamp or thumbscrew, respectively.
Choose a fret to place the capo on. If your banjo is tuned to Open G tuning, place the capo on the second fret to play in the key of A. Place a capo on the fourth fret to play in the key of B.
Hold the bar of the capo above the fret (between the metal frets) and tighten the capo using the elastic band, clamp or thumbscrew. Make sure the capo's bar is pressed hard against the strings and that the strings are not bent up or down under the pressure of the capo. A loose capo will result in a muffled sound, and bent strings will sound out of tune.
Place the capo's bar close to the metal fret without touching it. Placing the capo directly between two metal frets, closer towards the banjo's headstock or on top of the metal fret will result in a muffled, muted sound.
Decide on a method to change the tuning of the fifth string, if you play a five-string banjo. Tune the string using the tuning peg to fit the new key, hook the string beneath the head of a model railroad spike driven into the fretboard or use a fifth-string capo.
Tune the fifth string up two semitones — from G to A — if you are using a capo on the second fret. Tuning any higher than A can cause the fifth string to snap.
Hook the fifth string onto a model railroad spike driven into the fretboard by bending the string and catching it on the spike, if you have these spikes installed on your banjo. Railroad spikes are typically installed on the 7th and 9th frets, and hold down the fifth string against the metal fret in the same way capos do. Hook the string onto the 7th fret spike if your capo is on the 2nd fret, or onto the 9th fret spike if the capo is on the 4th fret.
Use a fifth-string capo. Fifth-string capos are installed onto banjos to hold down the fifth string on any of the fifth string frets. Slide the fifth-string capo to the fret you want to hold down and tighten the thumbscrew.
Using spikes may make the fifth string slightly sharp. Adjust the fifth string tuning if necessary.
Have your railroad spikes and fifth-string capo installed by a professional to avoid damaging your banjo, unless you are familiar with installing these banjo accessories.