Al,
A good trick is to set up your alternate sound on a volume pedal. I used to have piano as my main sound and then add either organ or strings that could be brought in with the pedal. I grew to call these "color sounds" because they would add color to the original sound,but not be a permanent part of it.
Brass hits can probably be layered with the piano with almost NO detectability, as well as organ. The Tyros can accomodate 2 layers on top of a staple sound, so set up a few patches and you're set to go!

Here's a few good "meat & potatoes" patches that comp well with great expression, as you add the pedal sounds....

R1-Piano
R2-Strings
R3-Organ

R1-Rhodes
R2-Organ
R3-Brass

R1-Organ
R2-Brass
R3-saw type synth(really fat)

Depends on how the other guys in your rhythm section carry the ball. You should be able to get along quite well with just the single kb. A little planning and you'll be sittin' pretty. Hope the knee heals up quickly too !