A universally familiar tune is the subject of an unusual copyright battle.

Yesterday, Jennifer Nelson, a documentary producer, sued the publishing arm of Warner Music Group for claiming it owns the copyright to “Happy Birthday to You,” the most recognized song in the English language. Nelson is directing a film about the song and had to pay a $1,500 licensing fee to use it.

Nelson’s suit claims “Happy Birthday to You” has been in the public domain since 1921; it seeks class action status on behalf of anyone who has had to pay a royalty to use the song in the past four years.

According to the Wall Street Journal Law Blog, “Happy Birthday to You’ nets Warner $2 million each year in licensing fees.

Read the New York Times for more information.

For more strange suits from InsideCounsel, check out our latest slideshow, “5 of the strangest lawsuits making headlines.”