The old joke is that the most important thing is sincerity, and once you learn how to fake that, you've got it made. That's sort of what Ella Fitzgerald accomplishes in "A-Tisket, A-Tasket" -- using the most sophisticated technical skill to create not just the illusion, but the actual presence, of pure innocence.
Which means it is an illusion, of course. Real pure innocence is something like Rebecca Black's "Friday." But the illusion is complete. There's no knowing wink. Well, maybe there is from Chick Webb's band, but even the band succumbs to Ella's innocence.
How difficult is this to achieve? Well, consider the era. We always look back at any era as "a more innocent time," but times are never innocent. This was a complex moment in time. It was the Depression, and people were longing for innocent optimism. The biggest star of the decade was Shirley Temple, of whom her distant cousin Franklin D. Roosevelt said, "It is a splendid thing that for just fifteen cents an American can go to a movie and look at the smiling face of a baby and forget his troubles." Shirley Temple's appeal was that she tried to be smart and sassy and grown-up (i.e., sexy), but she couldn't be anything else but innocent.
But there'll always be a reverse side to the coin of innocence. As Tex Avery pointed out, what everyone really wants to see is Red Riding Hood in bed with the wolf. And just as repressed Victorian England produced some of the most elaborate pornography, the era that made icons of Shirley Temple and the chaste romances of Fred and Ginger also did its best to get Red Riding Hood in bed with the wolf.
And as society's outcasts are also society's id, the escutcheons of hot sex and sexual innuendo were borne by African Americans, whether they liked it or not. Bessie Smith wasn't crazy about continually being asked to sing songs of sexual innuendo, but that was what the public, and the record companies, wanted. And jazz was associated with sex. If the stories of jazz being the music of whorehouses were overblown, that was still the perception. So the presupposition was that anything sung by a black jazz singer would carry a subtext of sexual availability.
It's been said that any object can be a metaphor for sex, and I should know. I've used most of them. And any concave object, a purse or a pocket, can be a metaphor for the vagina: viz., Bessie Smith's "Need a Little Sugar in My Bowl." And Ella sings a song about losing her basket, which a girlie picks up and puts in her pocket. Imagine Alberta Hunter singing that lyric. Imagine Lucille Bogan singing it.
And you can start to get an idea of Ella's accomplishment. Never mind her incredible musical skills, her ability to use her voice as an instrument, her overall understanding of music that enabled her to take over the leadership of Chick Webb's band after his death. In this song, she breaks through a nearly unbreakable stereotype. She makes innocence swing. She doesn't get in bed with the wolf.