Konstatin's thoughts on how to make a good jam!
USEFUL TIPS AND INSTRUCTIONS FOR FELLOW MUSICIANS
STEPS
Do sound checks to determine sound levels. See that musicians are comfortable with their sound levels to prevent "volume-ups" in mid-jam. Musicians who can't hear their instruments are known to crank up the volume gradually, and the result is a sometimes unwelcome escalation of sound. Make sure levels are set before you begin an open jam. Tune your instrument. Really. Do it.
- The percussion typically begins by just keeping time with a simple rhythm. As the jam progresses the percussion will build up in complexity and intensity bringing the entire band with it. The other instruments follow the same pattern from simple to complex. Make sure that you have a solid rhythm section (bass, drums and other chordal instruments). A bad rhythm section is worse than none at all. Make sure your drummer and bassist don't drop the tempo or turn the beat around.
- Start with general chord progressions. The host or jam leader can let everyone know what key to play in and whether there will be specific chord or key changes. It is a good idea to start simple and as you get more comfortable with more complicated progressions.
- Use easy, familiar cover songs for jams. Try songs you think everyone is familiar with as starting points for a musical collaboration. That way, you don't have to pick chord progressions; musicians who recognize the song will already know what they are.
- Find ending points and breaks. Generally speaking, it's much easier to get a jam started than to end it. When musicians have found their groove with an open repeating progression, they tend to stick to it for a good long while. If your jam is based on a song, there's a definite end point, but if not, someone's going to have to create one. A host or jam leader can use body language to cue the ending riffs or "wind down" on their instrument to signal an end to a jam piece.
TIPS
Listen to what the other musicians are playing/singing at all times. It is a good idea to not have every instrument playing the entire time. Have chordal instruments take turns comping for the soloist. If everyone plays constantly, it is very easy to lose the tempo or drop the song entirely, and the session gets boring fast.
Communication and cues. When jamming, constantly look at other players, their eyes and their body language. There is so much, musically, that you can make happen this way. Breaks, modulations (sometimes yelled and the end of a song section), solos, vamps, all these things are only possible when the players make eye contact regularly.
Singers. If a singer joins in, this generally pulls in the attention of the audience. Take shorter solos and let the singer shine! Don't play too loud, singers need to hear their own voice in order to sing in tune. A good singer will also give the band subtle cues or signs through his/her body language.
Respect your fellow musician. Most of the etiquette on jam sessions comes down to having a certain amount of respect for the abilities, but more importantly, for the FEELINGS of the other people involved in the session. Keep in mind that they might feel just as happy/unhappy/scared/hyped/out-of-place or whatever as you do. Also try to show musicians respect even if they act bossy.