A walking, talking clarity issue. A member of a marching band (particularly the drum line) in which no note is ever clear, giving a sharp contrast to the percussive rhythms created by the snare and tenor line. 3-5 drums tuned to different notes and muffled, most often used in runs in which, while the rest of the band is playing, are heard 'below' the winds. Being described as 'off the chain' or 'sick' while in a bass line is commonplace, and should be treated as such.
The 1989 Santa Clara Vanguard bass line was 'off the chain.'