As I enter the ice cream aisle of Trader Joe's (looking for mochi ice cream, of course), I hear Brenton Wood's 1967 soul classic "Oogum Boogum Song" echo through the store. I turn and see a mom singing the chorus to the baby attached to her. The baby and I both smile. I stall in front of the frozen desserts, also picking up chocolate covered bananas, not wanting to cut this beautiful moment short.

The rest of the music I heard in-store that Tuesday evening could also be categorized as classic soul, including The Sapphires' "Who Do You Love," The Ikettes' "I'm Blue," Al Green's "How Can You Mend A Broken Heart," Donny Hathaway's "The Ghetto," and Aalon's "Rock ‘N’ Roll Gangster." The soundtrack offered a nice, warm sonic ambiance and made spending over 30 minutes in the compact store less stressful.

Emma, a young, bubbly employee there—someone who spends a lot more time with the store’s music—also enjoys it. "For the most part, it gives me a pretty good vibe," she tells me. The fun, non-pretentious mix of music feels on brand with the Southern California-founded company's laid-back Hawaiian print-flocked image.

Each store has a few preset commercial radio stations to choose from, which Emma says, for this Silverlake, East Los Angeles location, "varies from day to day, but mostly they play surfer kinda vibes, sometimes a little bit of rock. And there's some days where we play heartbreak love songs, like Alicia Keys' 'No One.' That plays a lot here."

Typically, if you're having fun somewhere, and the people around you, including the employees, also seem to be enjoying themselves, you want to stay, even if things get a bit crowded or there's a line. Perhaps grocery stores are the unsung all-ages, family-friendly clubs. Perhaps your local wedding DJ could add a bit more energy to stores, but just as a DJ selects the right tunes to keep the energy moving, there is a methodology behind what stores play to keep you happy, shopping, spending, and returning.

What is the perfect music to play in a grocery store, that keeps employees and customers happy, and even encourages the latter to add a few more things to their carts?

One of the earliest studies researching how music affects grocery store shoppers was published in 1982 by Ronald E. Milliman in The Journal of Marketing, and is widely cited to this day. The study made the case that management thoughtfully selecting music will likely have a positive impact on the employees and customers, and that slower tempo music caused the latter to spend more time in the store and spend more money. Cue the Alicia Keys and Motown ballads!

In 2011, Klemens M. Knoferle built upon this research and also explored the mode of the music. There are seven common modes, or "collections of scales," used in popular music, with the major modes sounding happier and brighter and the minor modes darker or more melancholy. He noted that human's ability to perceive and process tempo and mode "is often considered universal or hard-wired."

Surprisingly, other research done between the two studies didn't focus on traits of the music itself. His work found that the best musical composition for longer time spent in store / higher store spending was slower tempo (below 95 BPM) in a minor mode, although music in a major mode was not impacted by tempo. An example would be Alicia Keys' "Fallin'," which uses Aeolian mode (the natural minor) and clocks in at just 63 BPM.

At Lassens, a local health food store, their Thursday afternoon soundtrack was soft rock ala Captain & Tennille's "Love Will Keep Us Together," Juice Newton's version of "Angel of the Morning" and Kenny Loggins' "Meet Me Halfway," with a little spice from the Mary Jane Girls' "Boys." I spoke to Iury, who works there and was enthusiastic about the music, sharing that he always notices it and really enjoys it, and has even discovered some good tunes he'd never heard before.

"Usually it's pop, retro, like '80s. Sometimes they play some soul, sometimes they play some house at night. Sometimes it's world music, like reggae, instrumental," Iury explains. He notes that it's usually set on the same station for about two months, except for December, when they play Christmas music. He says customers definitely notice the music as well, especially when they play disco or holiday tunes.

Yaprak Unsalan, the Managing Director of Jukeboxy, a platform that provides curated, licensed music to businesses including grocery stores, said "it's important to match the music with the products you are selling. As an example, our Italian gourmet grocery store customers always prefer Italian pop music in different energy levels for different times of the day and mix it with the Rat Pack and similar artists (Frank Sinatra, Dean Martin, Sammy Davis Jr., Joey Bishop)."

This is based on research from a 1999 wine shop study that found playing French-style music one day and German the other led customers to purchase more wine from the respective country. Unsalan adds that "Regular, busier supermarkets usually play '80s to present day pop, '80s soft rock, and sometimes '60s and '70s pop," which tracks with what I heard at my local Trader Joe's and Lassens. She also noted the importance of tempo and "familiar music [which] makes people happy" and makes them "feel more connected with the brand" and thus "finding the right balance between calming and familiar music."

For stores in large cities, the playlist may have to cast a wider net to feel familiar for everyone who walks through their doors. "In most diverse cities like New York City, Houston or Los Angeles we see the same trend; grocery stores mixing multiple playlists in the scheduling tool from different genres and decades to match their diverse clientele," Unsalan explains.

For its grocery store clients, Jukeboxy offers personalized playlists that can be updated, as well as over 350 hand-curated (i.e. not by an algorithm) playlists, which is what many choose. A search for grocery store music shows several companies that offer similar services, and as most grocery stores play music, this is clearly something they're thinking about. (To play music at a business, it must be licensed, meaning someone can't just put on their Spotify and call it a day.)

While there's plenty of research that supports the idea that the right music can improve grocery stores' bottom lines, the German-based affordable mart Aldi, which has 1,600 stores Stateside, opts out of playing any music to save money and keep costs low. It's the same reason Trader Joe's has tiny parking lots.

Here's to good tunes whenever you fill your cart with delicious food!