It is someone who's vocal range can cover a range of octaves, I think it is usually at least 2... Hope this helps :)
English voice: Maile Flanagan. Japanese voice: Junko Takeuchi
Jason Steele does the voice for charlie. He also does the voice of every other character.
Jalil Nelson from Fresno California, does the voice for riley, and the voice for huey possibly.
Yes
Bass voice