For the midi keyboard previously mentioned in yesterday's post/question -- Arturia MiniLab mkII;http://downloads.arturia.com/products/minilab-mkII/manual/MiniLabmkII_Manual_1_0_7_EN.pdf
When this keyboard is powered on, it defaults to Keyboard Preset 1 which is a special configuration for Arturia's Analog Lab software. Note that 'Preset' in the context of the keyboard is separate from the soundFont 'Preset', so I will just call this the 'mode'. In that default 'mode' 1, when one attempts to change the 'Midi Channel' by pressing the Shift button and one of the keys starting with the lower F, this does not change the midi channel, at least as reported by FluidSynth's debug output (key up/down mesages). This is the main reason I was looking for some alternative way to change the SoundFont preset from the midi controller.
However, by selecting one of the other modes 2-8, at least as they are defined by default, the midi channel can be changed. The modes on the keyboard are selected by pressing the Shift button and one of the pads.
Now that I have identified a way to change midi channel from the keyboard, it is easy enough to use the 'select' command to configure a different soundfont preset for each of the 16 available channels. In the fluidsynth shell/command file, this looks like;
# select <channel 0..16> <soundfont_id 1..n> <bank 0,8,9,16,128> <program/soundfont_preset 0..127>
select 0 1 0 0 #Yamaha Grand Piano
select 1 1 0 28 #Electric Piano
select 2 1 0 18 #Rock Organ
select 3 1 0 40 #Violin
select 4 1 0 42 #Cello
select 5 1 0 19 #Church Organ
select 6 1 0 9 #Glockenspiel
select 7 1 0 36 #Slap Bass
Now that I have access to 16 presets/voices/'programs', I have become less interested in trying to modify the soundfont preset, which is apparently the same as the 'prog'ram in the 'select' or 'num'ber in the 'prog' shell command. It might still be interesting to select a wider range of more than 16 presets using the CC dial, though on the particular controller, these are sensitive, and it would be fiddly to adjust +/- 1. I expect that the concept of tying a CC to the program/preset is at odds with general midi concepts, even though it should be possible in a piece of software.
I thought replying to my own question might be useful to some other relative newcomer, and of course save a senior subscriber the trouble of kindly taking me to school. I could prepare a PR for the github wiki material to include this example if others think it is warranted. Akin to:https://github.com/FluidSynth/fluidsynth/wiki/ExampleCommandLines
Thanks to the members of this community who contributed to development of this useful, flexible and of course entertaining software, apparently over almost two decades!