How do I create a custom voice, and can its tone be changed?

In 'Way Of The Nether' and other mini games a voice comes on and says something like "you'll never save your precious mayor". How do I define my own voice and include it in my game?

I've tried /say /tell /w /whisper but nothing seems to work

Pocket Edition version 1.16.40

Voices cannot be generated in vanilla Minecraft. They are custom sounds added by mods.

All the commands you tried are for printing messages in the chat. /playsound is the only command that can play sounds, and it can only play predefined sounds. You will need to add your own voice as a custom sound using add-ons.

I'm not much of an expert in modding Minecraft, so I'm not the right person to ask for the job. Check out info on add-ons if you want to explore this path further, or you can wait for the next answer from a more experienced Minecraft modder.