Paul McCartney shows his jazz-pop musical roots in new PBS documentary

WONDER WHERE the old-fashioned heart and humor at the core of Paul McCartney's music came from?

Answers can clearly be found in his recent foray album into jazz-tinged American pop standards, "Kisses on the Bottom," featuring ditties like "Ac-Cent-Tchu-Ate The Positive." This is music McCartney was spoon-fed as a Liverpool lad, "especially at New Year's Eve parties at Uncle Joe or Aunt Jan's where they'd roll the carpet back, get the piano out and sing all these songs," he recalled.

Friday, you can hear more about McCartney's roots on a "Great Performances" special, "Live Kisses" (WHYY-TV 12, 9 p.m.), recorded at the famed Capitol Records Studio A where his standards set was etched. It reconvenes the same crack team of (mostly) jazz-rooted backup: core pianist Diana Krall, guitarists John Pizzarelli and Joe Walsh and a lilting string section - all helmed by producer Tommy LiPuma and ace engineer Al Schmitt.

Shot for "period" effect in black and white, the live performance component was first delivered to viewers in February as a streaming iTunes concert event.

For the "Great Performances" rendering, director Jonas Akerlund has cut out a few numbers (drat) and added documentary footage - snippets of McCartney and his bandmates in rehearsal and ruminating about it all. Krall marvels how McCartney "has a great feel" for the material. Walsh says, "It's a different Paul than we all know, and it's wonderful."

Longtime McCartney fans may be taken back by the lightness of his vocal tone, at times verging on frail as he delivers the tender themes of "Always," "More I Cannot Wish You" (from the Broadway score for "Guys and Dolls") and "Bye Bye Blackbird," which may have sprang his variation "Blackbird."

The piano-tinkling showman Fats Waller remains a fave for McCartney. "I loved his sense of humor and rhythm and musicianship," he says. The special and album offer a double-dose of Fats: "I'm Gonna Sit Right Down and Write Myself a Letter" (from whence came the slightly naughty album title) and the jaunty "My Very Good Friend the Milkman."

While cut from the PBS version, McCartney's flub and restart of the latter made for a particularly honest moment on the iTunes special: Paul keeping it real.

Oh, and just so you won't think McCartney was out in the ozone alone with this nostalgic music, he allows, "John [Lennon] and I bonded over this kind of stuff" and applied a similar aesthetic to Beatles songs "like 'Nowhere Man.' "