Jam. Band. Apart, these two words are innocuous. Put them together, and they somehow become polarizing. Whatever your perceptions may be, there are a few characteristics that help give meaning to this loosely defined genre. First and foremost, the artists are expert musicians, masters of their instruments and playing styles. These bands are also marked by their relentless touring schedules, which naturally lend itself to the improv that is a hallmark of the live setting.