… make sure you are listening/monitoring on good speakers or headphones so you can accurately hear what it sounds like.
Start there. There’s nothing quite like doing a mix on your laptop speakers, or headphones you bought at a record store on vacation (raising hand) and then hearing it later on a good system.
I was on vacation, not the record store.
Step One, search out voice pitch changing software. I don’t think you’re going to get Audacity to do anything theatrically acceptable. As above, general pitch shifting changes everything and human voices don’t work like that. For example, if a very large man and a small girl whisper at you, you won’t be able to tell which is which. But the instant they say some real words, it’s obvious. “S”, “T”, and, “CH” sounds can’t change, but everything else has to, and then the new combination has to sound natural.
Good luck. Post back if you find something you like.
A note: Tenor speaking voices are not the worst thing. They can cut through challenging listening environments. Overly bassy “broadcast” voices can get lost in the rumble. Also see: listening while running on the beach. “I can’t understand the performance over the surf and the player volume won’t go up any higher.”
Another note: All these tricks are only going to work if you shot the original voice in a studio. Did you use a good, echo-resistant, quiet room? If you have talking-in-a-milk-jug or bathroom reverb in your voice, these tricks and changes may have some nasty surprises.
You’ll have to remember to make your chosen changes to every performance before anyone hears it. Are you up for that? The audiobook people get stuck with this. Wait, you mean I have to stop and correct every chapter?
And then way down the line, when you become famous and popular, someone is going to want you to do a live performance. Won’t that be messy?
If you feel like it, post a real example of your voice.
Use this formula.
https://www.kozco.com/tech/audacity/TestClip/Record_A_Clip.html
Koz