/b_setn                               Set ranges of sample value(s)

int       - buffer number
[
  int     - sample starting index
  int     - number of sequential samples to change (M)
  [
    float - a sample value
  ] * M
] * N

Set contiguous ranges of sample indices to sets of values. For each
range, the starting sample index is given followed by the number of
samples to change, followed by the values.