[sdiy] Group Level Shift?

[Michael Ruberto]

I have 3 separate signals that I want to level shift at the same time from 
one switch. The signals are all +/-5. I want to have a toggle switch that 
will shift the signals to 0 > +10, -5 > +5, and 0 > -10. Of course I want to 
do it as economically as possible. Can I do it by simply adding a bias 
resistor to the inverting input of an op-amp, plus the signal, and using a 
switch to connect that resistor to either - rail, + rail or nothing?
keep in mind there would be 3 op-amps - 1 per signal. If I connect the bias 
resistors to the center of a SPDT switch will I get bad interactions between 
the 3 channels when the switch is in the "off" position? Should I be looking 
at a 3PDT for this?
Does this even make sense?

Thanks

M. A. Ruberto