One of the most familiar songs to all Americans could soon be free to use if a federal judge rules against Warner Music Group's decades-old grip on the rights to "Happy Birthday to You."

Judge George H. King heard arguments Wednesday in a case that pits the publishing arm of Warner Music Group against New York-based Good Morning to You Productions, which is making a documentary about the 1893 ditty.

The question comes down to whether Warner Music Group can continue charging for the use of the song or if it is in the public domain and free for all to use.

King said at the start that he would not immediately rule on a plaintiff's motion asking him to declare that the song is in the public domain and no longer subject to licensing fees.

After Warner asked the documentary makers to pay $1,500 to use the song, Good Morning to You filed a class-action suit in 2013, arguing the song was in the public domain.

Warner has pressed its copyright claim since it purchased the Birch Tree Group in 1988, the successor to the Clayton F. Summy Co. that previously held the rights.

As it stands, Warner can charge anyone who wants to sing or play "Happy Birthday to You" as part of a profit-making enterprise. This most often occurs with stage productions, on TV, in movies, in ringtones or in greeting cards. But even those who want to sing it publicly as part of a business technically have to pay for permission to use the song.

The plaintiffs argued in a court filing this week that the copyright for the song expired when both versions of the song were published in the 1922 "Everyday Song Book."

Warner attorneys disagree. They argued in a document filed Tuesday that Jessica Hill, who had inherited part of Mildred Hill's rights to the song, renewed the copyright to "Good Morning" in 1921, and that the "Happy Birthday to You" song was copyrighted by Summy with authorization from the family in 1935. Summy renewed the copyright in 1962, decades before Warner Music bought Summy's company.

Los Angeles Times