AKA "HOW MANY STRINGS SHOULD MY BANJO HAVE?"
What is the difference between four, five & six string banjos? If you want to play banjo and you don't know the answer to this question, you should! This is a very important question because the type of banjo that you play will be determined largely by the type or style of music that you want to play.
The 4-string banjo is called a tenor or plectrum banjo and is generally used for dixieland music. It is played with a guitar pick. (Another word for pick is plectrum, hence the name plectrum banjo...) You can either play and strum chords as backup, or you can actually pick out the melody notes like what you would do on a guitar. The standard tenor banjo has 19 frets. The 17-fret tenor banjo is called an Irish Tenor banjo. Both of these tenor banjos look about the same size as 5-string banjos.
There is such a thing as a longneck tenor banjo. It has 22 frets rather than the shorter 17-fret (Irish) or 19-fret tenor banjo. The longer neck length gives the banjo a deeper (lower) pitch.
You also might see small four string banjos. These are actually banjo ukuleles. They can be played like a standard ukulele, or just like a tenor banjo as well.
The tuning on a tenor banjo can vary greatly. There are quite a few different tunings that are used. I don't play much on tenor banjo, but when I was talking to some of my fellow friends who play tenor, they told me that at the St. Louis Banjo Club, everyone uses different tunings to suit them according to what is easier for them to finger, or what might be similar to the tuning used on another stringed instrument that they already play. Some people tune the tenor banjo like a fiddle or mandolin (EADG), some tune it like a ukulele (GCEA), and then there are others that tune it like the first four strings of a guitar (EBGD). Due to the fret spacing, I think ukulele or guitar tuning is the easiest to play chords from.
Standard 5-string banjos have 22 frets, with the 5th string tuning peg at the 5th fret. The 5-string banjo with a resonator is the standard for bluegrass banjo. It can also be used to play folk music or clawhammer (frailing). For clawhammer, you want a banjo without a resonator. This gives the banjo a softer sound both in volume and in tone quality. Bluegrass style banjo is played with a thumbpick and two metal fingerpicks. Clawhammer style banjo is played with the fingernails or special plastic picks that fit over the nails of the right hand. Think of Earl Scruggs for bluegrass style and Grandpa Jones (Hee Haw) for clawhammer style.
There is also a longneck 5-string banjo as well. The standard 5-string banjo has the 5th string tuning peg installed at the 5th fret, and has 22 total frets. The longneck banjo has three more frets than the standard 5-string, making the 5th string tuning peg at the 8th fret or between the 7th & 8th frets (depending on the maker of the banjo). Due to its longer length, it has a lower tone than the standard 5-string, making it more popular for folk music and frailing.
The 6-string banjo is basically a guitar that is in the shape of a banjo. It is tuned like a guitar and played like a guitar. This would be ideal for someone who already knows how to play a guitar, but wants the tone quality of a banjo. The important thing to note here is that since it will be played like a guitar, it will only have the tone quality of the banjo, not the sound of HOW the banjo is played. In other words, a 5-string bluegrass banjo will be played with rolls. There are many fast notes that fall into specific patterns. These cannot be duplicated with a guitar pick.