How would I make a gibberish-type voice?

How would I go about making randomized sounds that play as dialogue appears? Incase you don’t understand, I i mean like banjo kazooie, animal crossing, or kiwi64, does it have to be pre made sound or is it controlled in a script?

Probably there are many ways to do it. One way to do it is explained in this video quite good: Making Gibberish Text Sounds for your game - Unity Tutorial - YouTube