In 1993 an appealing idea took new parents by storm. Playing classical music to babies would make them smarter, according to a paper published in the journal Nature. The study showed that a few dozen undergraduates were marginally better at solving puzzles after they listened to a Mozart piano sonata. Massive press coverage followed.

The Mozart Effect, as it was called, became a marketer’s dream. Recordings packaged for infants flew off the shelves, even though the impact of Mozart on the college students’ problem-solving skills was fleeting, lasting no longer than about 10 minutes. Indeed, the so-called Mozart effect had never been tested in babies at all and could not be reproduced in adults, either.

Clearly, it pays to be skeptical about get-smart-quick schemes. But what if music does have a salutary effect on infants, one that is more about happiness than smarts? Every parent wants a baby who cries less and is easy to soothe. Now a new study shows that music can help—as long as it’s created with your own vocal cords.

The study, led by Eun Cho and Lidya Yurdum of the Yale Child Studies Center, looked at how often parents normally sing to their baby and whether that frequency could be juiced by a little music education and some electronic nudges. The researchers randomly divided 110 parents of 3-6 month old infants into two groups. Those in the experimental group were taught some simple folk songs using karaoke style sing-alongs, and were given a book of folk songs for children with lively illustrations, lyrics and pressable buttons. They also received weekly newsletters about music for 6 weeks.

Parents in both groups were prompted at random times to fill out surveys about what their babies were doing. Those in the music enrichment group reported that they had recently sung to their babies 89% of the time, compared to 65% for those in the control group. Clearly, when parents are given resources and encouragement, they are more likely to incorporate singing into their infants’ daily lives.

As for the babies’ response, those who were sung to more often tended to be calmer and less fussy. “It’s not that their mood increased due to the singing right then and there, like ‘singing made the baby smile,’” wrote Samuel Mehr, the senior author of the paper and an adjunct professor at the Yale Center. “The babies’ mood improved overall as a result of the intervention. Yet not many pediatricians are telling parents of fussy babies to sing to them.”

“Though singing is not as simple as playing music to your baby, it doesn’t take much,” Mehr said. “Parents know how to do it and the baby is not a tough audience. Singing to your baby really works and it’s a very chill thing to do.”

And unlike a Mozart-for-babies recording, it’s also free.