you can toggle between mt32 and soundfonts using sysex in mt32-pi

mt32-pi-control on github

to find ports use aplaymidi or aconnect then use this as the info for the -p option

aplaymidi -l



-g to change to soundfont 

mt32-pi-ctl -p 128:0 -g


-s to change --soundfont specify the number 

mt32-pi-ctl -p 128:0 -s 1


-m to change to mt32  

mt32-pi-ctl -p 128:0 -m


-b to change romset: old, new, cm32l 

mt32-pi-ctl -p 128:0 -b cm32l