"A Cauldron Full of Hot, Strong Love" by Celestina Warbeck 

2/17/18 at The Wizarding World of Harry Potter in Universal Studios Orlando
From the Harry Potter Wiki:
"A Cauldron Full of Hot, Strong Love" was a jazzy song performed by Celestina Warbeck. Arthur and Molly Weasley danced to it when they were eighteen, and, with their family, they listened to it again on Christmas 1996 on the Wizarding Wireless Network. Molly tried to get everybody to listen to the Christmas broadcast, but nobody except Molly enjoyed it, as Fred and George played Exploding Snap, Fleur Delacour thanked goodness that it was over when it ended and Arthur apologised to Harry about the broadcast, promising it would be over soon.
When Ronald Weasley tried to guess the password to Potterwatch in 1997, A Cauldron Full of Hot, Strong Love was heard a few times.
Source: harrypotter.wik...