How are monsters howling in movies and games made?

The monster roar in movies and games is basically synthesized by the sounds of various animals. ? Let's take a look at a tidbit of the World of Warcraft collector's edition. The video introduces the sound synthesis steps of the death of the blue dragon. Among them, the first seven tracks are the independent tracks of the roaring of real actors and beasts, and the last one is the final sound after synthesis. The first few tracks of this video use real actors (actually employees of Blizzard ...), followed by tigers, lions, brown bears and other beasts. Many movies also use large animals such as elephants and whales, and may add sound effects such as metal collision, wind whirling, waterfalls and running water as an aid as needed.