Combining two bass signals together?

[kiat]

My wireless bass received has two 1/4" TS outputs and I'm thinking of running them each through separate signal paths, then recombining them post-processing into a single mono signal, to emulate two separate basses playing in unison, perfectly or imperfectly. E.g. "Walk on the Wild Side", "I Want You Back", "Black Dog".

 

I read that a y-splitter cable would need radiators to prevent the mono signals backfeeding each other.

 

What equipment would be needed? Is a box doing this already? Can an AB pedal combine?

[kiat]

They'd be combined into one mono signal for my amp and FOH, though likely not for the IEMs.

 

If it's not clear the idea is to experiment with a single bass to sound like two basses, where each bass gets a different sound from effects etc.