The 73-year-old actor - who was 42 when the first film in the franchise opened - admitted he "didn't know how to take" the notes he received after his first recording session, but learned the importance of warming up his voice.
"Early on when we did this first radio plug for this one, T5, in a nice way some of the engineers were going, 'Buzz sounds a little old,' and I didn't know how to take that," he told Entertainment Weekly.
"So I got together with a voice coach from New York City Opera [that] they put me with. She said, 'You're not old. Don't get that in your head. You do have to warm up at your age. You can't just get right into [it].'"
Allen noted there is a "very specific modulation" of playing Buzz.
"It doesn't seem very different than the one I'm speaking in, and there were some vocal exercises," he said.
"I don't know why. Maybe it's because I'm 900 years old now. And with some vocal exercises that opera singers do, Broadway people - that's a lot of exercise, so I had to learn the process of warming up."
Meanwhile, co-star Tom Hanks, knows the best way for him to produce cowboy Woody's distinctive tone.
"I have to get out of my neck and come from the diaphragm 'cause that's all Woody does!"
Hanks recently admitted he can't believe he's "still a part" of the Toy Story franchise more than three decades on from the release of the first film.
"I have seen it. I don't know how they do it, but it is a vibrant and proper chapter in the Toy Story canon," he said.
"None of us can believe that we're still a part of it."
Asked to share some details about the new movie, the actor replied: "Oh my Lord, all I can say is the saga continues."
However, an official synopsis for Toy Story 5 teased some details about the new film.
The synopsis reads: "The toys are back and this time, Buzz Lightyear, Woody, Jessie and the rest of the gang's jobs are challenged when they come face-to-face with Lilypad, a brand-new tablet device that arrives with her own disruptive ideas about what is best for their kid, Bonnie. Will playtime ever be the same?"
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