I have my guitar with me along with a Pod pedal which creates mutiple sounds such as reverb, echo, chorus to name a few.
Along with my Apple laptop I am able to lay down recorded
tracks that I use as background when I play out.
A silent viola is comparable to an electric solid body guitar.
It may not even have a body at all, just a neck joined to
a wood shaft that has the peg attached.
It is silent because the viola, which is an acoustic instrument, needs the body to project the sound.
No body, then only a slight tone is heard from the strings.
But they usually have a headphone pre-amp built in so you can blow your eardrums out playing TSO.