Combining Time Signatures

Hello,

I wanted to ask if themes from two different time signatures, namely 9/8 and 6/8, could be combined in the same piece. And I'm speaking of the stable parts, not a fast vituoso or something like that. 

Thanks ~

...at the same time?  Sure. 

In different places?  Absolutely.

You can do whatever you want.

What?!? Heresy!

Or rather, lolwut?

Too late.

Now just you wait one goshdarn minute, who do you think you are?