Sebastian is a fox who has run showbusiness for a short time. In the sequel, he is now apart of the bigger picture of film production.  He is very sassy and a busy body yet he has a sternness to him.

Here is a reference for his voice to better understand her tones and such:  https://www.youtube.com/watch?v=e7WAXVxifoA 

You must have discord as well as a decent microphone set up. As for other requirements being capable of singing with the voice and express emotion with the lines if need be. You do not need to be exact,  just recognizable to fit the character.