fluidsynth/doc/polymono/poly_mono_4.txt

# How to change an actual basic channel and add a new one ?
# ---------------------------------------------------------
# Note that command setbasicchannels allows to add or change
# groups of basics channels.
# 
# Note also that the commands allows this for more than one
# groups executing only one command:

# The following command restores Group 1 to the state:
# -Group 1:Basic channel:  5, poly omni off(mode 2), nbr:  1
# Then adds a new group:
# -Group 0:Basic channel:  2, mono omni on(mode 1), composed of 3 possible channels in this group 

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

# Use command setbasicchannels to change a group and add a new one, using numbered mode 2 and 1:
setbasicchannels    5  2  0    2  1  3
# or using named mode:
# setbasicchannels    5  poly_omnioff 0    2  mono_omnion 3

# Use basicchannels command to verify your settings
basicchannels

# end