Do I need two of the same RAMs to operate a desktop?

Do I need two of the same RAMs to operate a desktop? I have a Lenovo H530. 4gigs of RAM obviously. I'm looking to upgrade it but I have little knowledge of it. If I wanted to install one 8gb RAM but leave the second one there. Will my desktop still operate? Is 2 8gig rams necessary or 2 4gig rams? I do video/music production, I'm tired of the waiting time for loading, rendering, etc.

It will work but sometimes it will run the ram in single channel mode instead of daul channel, meaning instead of having 1333mhz ram speed you will have 669mhz ram speed.

2 different pairs of ram and my pc and it works fine

No its not necessary