One of the primary reasons that many people want to learn to play the banjo is to have fun making music with others in bands and in jam sessions. There's nothing quite like a banjo, guitar, mandolin, fiddles, and bass grooving along to an old, lonesome-sounding ballad or burning up a hot, fast instrumental.
At a music festival, seeing amateur musicians who have never played together before open up their cases, take out their instruments, and start playing tunes together as if they've been doing it for years isn't unusual. Musicians call these impromptu get-togethers jam sessions.
Musicians can play together in such a spontaneous way because they share a similar repertoire of songs and have internalized and put into practice some rules for effective group music-making. If you listen closely to a great bluegrass or old-time band performance, you can hear that the roles of the different instruments seem to change from one moment to the next.
At times, the banjo is out front and the center of attention; other times, the banjo is very much in the background; and then you recognize those moments when the banjo is somewhere in between these two extremes. When playing with others, you assume different musical roles with your banjo as you play a song from beginning to end.
For every moment that you're the star of the show as a banjo player, you'll have many more occasions when you give it everything you've got to make those around you sound their best. Backup playing includes all the different techniques that a banjo player uses to accompany others and is perhaps the highest achievement of great banjo playing.
Because the banjo can so easily overpower other instruments during a jam session or in a band, a simple chording technique is sometimes the best way to allow others to be easily heard, especially if a singer is singing quietly or if you're playing backup to a guitar or mandolin solo (which never seem to be able to pick up as much volume as the beloved banjo). Bluegrass musicians call this chording technique vamping.
At other times, you want to keep a steady flow of notes going with the banjo, changing chords at the same time as other musicians. With this kind of backup (which sounds especially good when accompanying a singer or a fiddle solo), you're keeping the energy flowing by doing what the banjo does best with roll patterns and basic accompaniment techniques.
Perhaps the two most important aspects of playing with others are to maintain a great rhythmic groove that makes the band sound good and to control your volume. The easiest way to achieve good rhythm is to play simple things well. Your right hand not only controls your volume, but also communicates the heart and soul of your playing.
Simplicity and drive in your playing creates musical space for others to play their best and for you to express your own emotions most powerfully. A successful jam session is one in which all musicians feel that they're successfully contributing to the overall sound of the group.