Researchers found, when the baby looked away from the face, the music stopped and a new sad song would start. On the other hand, the babies stared at the face three to four seconds longer, when the happier “Ode to Joe” played. Babies as young as 5 months can distinguish an upbeat tune, like “Ode to Joe” from Beethoven’s Ninth Symphony, from a lineup of gloomy tunes. Flom said, “One of the first things babies understand communicatively is emotion, so for them the melody is the message.” Their study showed that by nine months, babies are categorizing songs as happy or sad the same way that preschoolers and adults do.”