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"We decided to keep it very simple, very organic, not go the big bombastic big band way, "Our approach was just getting into the songs, singing the songs like I actually meant them."

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To help him build an Americana album unlike others developed by musicians like Rod Stewart and Robbie Williams, McCartney enlisted the help of Tommy LiPuma, the Grammy Award-winning producer who's worked with the likes of Barbra Streisand, Miles Davis, Anita Baker and Natalie Cole.

"I met him in New york, and we were both interested in the idea," McCartney said. "We liked each other. I just started talking to him and he knew all the songs I was talking about and more, so he could suggest some to me, and he turned me onto some songs for this album. He's been producing for a long time, and we've got a lot of things in common."

LiPuma and McCartney said they enjoyed working together because they both took a hands-off approach with each other, but contributed ideas to making the other one successful.

"One of the good things about working with Tommy is that he sits in the studio, he doesn't go into the booth, so he's like an extra member of the band," McCartney said. "He'll be sitting there saying, 'You know, that groove was just a little fast. We're gonna try it a tad slower.' Sometimes we said 'yeah,' sometimes we said 'no,' but it was a nice way of working. It was good for us all, I think. We started to just have fun with it."

Yet, even with another experienced music veteran in the room, it wasn't enough. McCartney, who has performed on the world's biggest stages with The Beatles, felt overwhelmed by his current situation. He didn't know what his album should sound like.

"We came in this studio and I was in the vocal booth a bit intimidated by the whole thing because I've normally got a guitar or piano in front of me to protect me," McCartney said. This time, there was nothing, I was just standing up in front at a mic. I was very nervous about the whole thing, and then the engineer said to me, "You know that's Nat King Cole's mic?' And I said 'Ah.' That really put the pressure on."

To help McCartney find his desired tone for the album, LiPuma enlisted the help of Diana Krall, the jazz singer and pianist who has released seven multi-platinum albums, in addition to nine gold and three platinum albums, and who also won three Grammy Awards and eight Juno Awards for her work. Krall is one of the best-selling jazz artists of her time, and the only jazz singer to have eight albums that debuted at the top of the Billboard Jazz Albums.

"I think Tommy suggesting Diana Krall to play piano was a good thing," McCartney said. "Her dad loves all the old songs... and I found she was a great team player. She wanted to do this stuff the way we wanted to do it."

McCartney had planned on doing a jazz album someday, and some of "Kisses from the Bottom" has hints of jazz mixed in with classical Americana. Yet, singing an album of other people's material was ultimately difficult for the 69-year-old musician.