fluidsynth/doc/polymono/poly_mono_3.txt

# How to change an actual basic channel ?
# ---------------------------------------
# Perhaps you have already set several groups of basics channels 
# and you want change the settings of one.

# Assuming following actual groups:
# -Group 1:Basic channel:  5, poly omni off(mode 2), nbr:  1
# -Group 2:Basic channel: 10, mono omni off(mode 3), nbr:  1
# -Group 3:Basic channel: 13, mono omni off(mode 3), nbr:  2

# Now we want to change  group 1: 
# Group 1 should have the following settings:
# -basic channel 5, mode poly, omni on, (mode 0) composed of 4 channels in this group.

#First use the command resetbasicchannels to clear the group intended to be changed.
resetbasicchannels 5

# Then use command setbasicchannels using numbered mode 0:
setbasicchannels  5  0  4
# or Using named mode:
# setbasicchannels  5  poly_omnion 4

# Use basicchannels command to verify your settings
basicchannels

# end