Meghan Trainor is about a lot more than that bass

Ms. Trainor started the year as a behind-the-scenes songwriter but ended it as something of an accidental sensation thanks to “All About That Bass,” a song originally recorded on a whim for someone else — Beyoncé, maybe? — to perform. When labels balked at the demo, telling her they did not have the right delivery vehicle for the song’s mix of ’50s-inspired novelty doo-wop and bubble-gum hip-hop — “Yeah it’s pretty clear, I ain’t no size 2,” she half-raps, “but I can shake it, shake it like I’m supposed to do” — Ms. Trainor herself turned it into a body-positivity smash. (“That bass” refers to her lower end.)



The song quickly became a cultural phenomenon, the kind of catchy tune parents and children alike mouthed the words to, while critics considered the complications of its body politics. At the Jingle Ball, the Super Bowl of Top 40 radio, her newness was apparent next to performances by 2014’s other pop titans, like the sneakily self-assured Ariana Grande, the unsinkable Iggy Azalea and, of course, Taylor Swift, the reigning queen of them all. But Ms. Trainor was formidable company on paper, with “All About That Bass” having spent eight weeks atop the Billboard Hot 100 chart and earning a Grammy nomination for record of the year and song of the year. The video has been viewed more than 450 million times on YouTube. “Lips Are Movin’,” a follow-up with a similarly playful sound (and a reference to “this bass”), reached No. 4 on the charts ahead of the release of her major-label debut, “Title,” out on Tuesday from Epic.



Now comes the really hard part, as Ms. Trainor attempts to transform one megahit into a performing career — one not entirely dependent on the very young fan base she’s attracted thus far with her everygirl demeanor and bright melodies. Combining the retro sound and technical proficiency of Adele and Amy Winehouse (if they wore more pastels), with the relatively safe, singsong rhymes of Ms. Azalea (sans the rap music signifiers), Ms. Trainor is a musical chameleon, fluent in many styles from her time as a hired gun writing for other artists. She also recently turned 21 and won’t pretend otherwise. “I didn’t want to be a Disney girl, or put in that category,” Ms. Trainor said over sushi at her downtown hotel the day before her brief arena showcase. “We didn’t know little girls would gravitate so much to ‘The Bass.’ ” Beyoncé recently told the singer that Blue Ivy, her 3-year-old daughter, is a big fan.



“Another famous girl tweeted me the other day: ‘Caught my son singin’ the song — too bad I didn’t catch him before the swear,’ ” said Ms. Trainor, who often drops her Gs and sprinkles curse words befitting her age in both song and conversation. “I said, ‘Sorry, boo, didn’t know the babies would love it.’” “Title” has the same innocent sound — rich throwback harmonies and handclaps, ukulele and rollicking acoustic bass — but also dips further into more ribald themes on songs like “Bang Dem Sticks.” “I ain’t talkin’ dirty,” she promises self-consciously, before revealing that her “drummer” can “play all night.” Other album cuts include “3 a.m.,” about late-night texts, and “Walkashame,” which Ms. Trainor says is based on a true story that includes an awkward 6 a.m. phone call to her father. (“He was like, ‘What are you doing up so early?’ ” she said.)



When the label asked for a cleaner version of “All About That Bass” to play on Radio Disney, Ms. Trainor and Kevin Kadish, who collaborated with her on that song and six others on “Title,” agreed, but only on the condition that it be relegated to the kid station and never put up for sale. “We didn’t want to water down what we had created,” said Mr. Kadish, who has previously written for Jason Mraz and Miley Cyrus. “She’s got a lot of responsibility right now,” he added. Thanks to the love-yourself-as-you-are message of her hit, “she’s a role model,” he said. “She’s just authentic.”



Still, even “All About That Bass” came with some controversy for its politics, which some took to be as retro as the sound — it is still, ultimately, about appealing to men and jokingly disses “skinny bitches” — and its racial appropriation. “I want to warn you that the entire song is sung by a white girl using a faux African-American vernacular accent,” the author Jenny Trout wrote on her blog. “As a feminist, I’m no longer content to watch women of color treated as props to further an appropriation of beauty standards that white women boast about and black women are oppressed by.”