You must set kit mode before attempting to change any kit items. We'll set it to 'multi'.

direct 1 64 58 0

Kit item 0 is always enabled, although you can mute it and enable/disable the individual engines.

To be clear though we'll enable kit item 3 and work with that so add 32 to the kit number.

direct 1 64 8 0 35

And set its minimum note.

direct 56 64 16 0 35

Then enable the subsynth engine.

direct 1 64 8 0 35 1

And now change its volume.

direct 40 64 0 0 3 1

Note you only add 32 for the kit item commands, not the engine internal commands.
