When Tony Bennett released Duets: An American Classic in 2006, the legendary singer figured it was a one-off project. Then the album debuted at No. 3 on the Billboard 200 and sold more than 3 million copies worldwideNot according to SS; get SS from Keith, which very well might be the same no., according to Nielsen SoundScan, and, Bennett says with a laugh, "I was almost strangled by Sony Columbia [to do another one]."

Actually, Bennett notes, the label said "please," and thus Duets II was born. The 17-song set, which arrives on Columbia on Sept. 20, features Bennett, who received the Billboard Century Award in 2006, singing alongside veterans Willie Nelson, Natalie Cole, Andrea Bocelli and Aretha Franklin, as well as relative upstarts Carrie Underwood, Michael Bublé, John Mayer, Lady Gaga and the late Amy Winehouse, who joined Bennett for "Body and Soul."

Duets II is a crown jewel in Bennett's ongoing 85th birthday celebration, which also includes upcoming performances at benefit shows at New York's Metropolitan Opera (Sept. 18) and the Staples Center in Los Angeles (Sept. 24), as well as the massive, 73-CD/three-DVD Tony Bennett-The Complete Collection, which arrives Nov. 8 exclusively at Barnes & Noble and TonyBennett.com.

1 You've collaborated with other singers throughout your career. What's the secret to a good duet?

Well, your voices have to contrast so that the public knows right away who's singing at the time. A good example is the album that Louis Armstrong did with Ella Fitzgerald [Ella and Louis; Verve, 1956], where she sang soft and sweet and he sang real craggy. There has to be a big contrast between the two voices.

2 Was there any difference between making the first Duets album and this one?

I must tell you that something good is happening. The new artists are coming out of schools like the Berklee School of Music in Boston, the Juilliard School. Lady Gaga is from NYU, and they're teaching the performing arts to students and it's a big help. When Rosemary Clooney and I started, the older performers like Jack Benny and George Burns would say to us, "You're doing OK, but it's going to take about six years to learn how to become a consummate performer," and sure enough, it took that time. But now the teachers are really showing them what to do and how to present themselves and how to be prepared. And it shows up on the record.

3 Speaking of Lady Gaga, what's she doing on a Tony Bennett album?

[Laughs] Well, I never met a more talented person in my life than Lady Gaga. She's going to become as big as Elvis Presley. I've been performing with different people my whole life, on the Sinatra albums and also with Lena Horne and all the great performers that were 10 years older than I was, and here she comes along and I'm telling you, she's the most talented person I've ever met. We have a lot to expect from her.

4 Duets II is getting a lot of attention obviously, and sadly, because of Amy Winehouse's death. What was it like working with her?

Everything that we did in the studio to make this whole record is on film, and I think it will surprise everybody as to how well we ended up getting along. She was a little apprehensive about how to go about it, and I just happened to say to her, "It sounds like you're influenced by Dinah Washington," and that just blew her mind. She said, "Oh, my God, you mean you can actually hear that? She's my idol! She's my favorite!" And I said, "Well, you're right, because she's a great singer," and that relaxed her.

5 You and Aretha Franklin singing together is a real meeting of the titans.

She was very, very professional. She's in top shape after her recent surgery. She looks great. She sounds great. She is such a good musician; she understands music intimately, and you can hear that on the record. She was very prepared and knew exactly what to do, so it was a real pleasure. Originally I wanted her to sing "Lost in the Stars," and she said, "No, I want to do 'How Do You Keep the Music Playing?'" And it was a good choice that she made.

6 What's the secret to durability?

I always play to the audience. I never thought about demographics young and old. I thought the biggest mistake the record companies ever made was when they split it up and said, "This is your music, and your parents like the other kind." I thought it was very ignorant because you should play to everybody. Whoever wants to come and hear and listen-that's an audience. I never worked with a demographic group. I never did rap music. I never did disco. I never followed the fashion. I just stayed myself and tried to only sing great songs. And it worked.