There may soon be a lot more birthday scenes on TV and in the movies.

Happy Birthday To You is no longer a song to be avoided by the entertainment industry because of hefty licensing fees to use the song. A U.S. judge ruled recently that the commonly sung tune belongs in the public domain. The ruling still could be appealed by Warner/Chappell Music Inc., which claims it owns the copyright.

But party-goers and well-wishers wanting to start a rousing rendition of Happy Birthday To You to celebrate their loved one should still feel free to sing the tune.

"I don't think they have anything to worry about either ... before or after this ruling," says Graham Hood, an associate who practises copyright law at Smart & Biggar/Fetherstonhaugh firm's Toronto office.

But, while a private version of the song at a birthday party may be OK, there are other murkier parts of copyright.

Canadian copyright law is "remarkably complex," he says.

For the most part, artists retain the right to publish, reproduce and perform their work for their lifetime.

They can pass on copyright to their estate or another person after they die. That person then holds the copyright for the rest of the calendar year after the artist's death and another 50 years. After that time passes, the work enters the public domain and is free from copyright restrictions.

Some musical works, like sound recordings, are subject to slightly different time frames.

The rules are contained in Canada's Copyright Act.

It's also filled with exceptions, Hood says, and then exceptions to those exceptions, making copyright infringement something that is often determined on "a case-by-case basis."

Below are some situations that could unexpectedly pose a risk of copyright infringement.

School concerts

Elementary schools often hold seasonal recitals for students' parents and relatives.

At holiday time, some classes may perform a rousing rendition of Santa Claus is Coming to Town or White Christmas. Unfortunately, both remain copyrighted and out of the public domain, according to the Public Domain Information Project, a site where users can search for royalty-free songs.

The Copyright Act offers special protection to educational institutions using copyrighted material, but only under specific circumstances. The performance must take place on school grounds, be for educational or training purposes, take place in front of an audience made up of mostly teachers and students, and not make a profit.

A court could look at whether the recital was truly educational, charged an admission fee or solicited donations, or if the audience was mostly students and staff, says Kevin Sartorio, who leads the Gowlings law firm's copyright law group.

YouTube videos

YouTube videos that play or cover another artist's copyrighted music can prove to be troublesome.

A copyright lawsuit over a YouTube video starring a baby bouncing along to Prince's Let's Go Crazy is about to head to trial. Closer to home, Toronto Mayor John Tory's parody video featuring a Kanye West song was withheld by Twitter, where he originally posted it, "in response to a report from the copyright holder."

Recently, Canada's act was amended to include a fair dealing exemption for non-commercial user-generated content, Sartorio says, like YouTube videos that play or cover copyrighted songs. Under the exemption, people can generally use the music so long as they don't profit from it, credit the people who created it and don't adversely impact the dissemination of the original work.

But if a video of, for example, someone covering Sia's Chandelier goes viral and the person adds a few advertisements that people must watch before the video plays?

"Then it would become a problem, probably," says Sartorio.

Weddings (in non-traditional venues)

Many weddings include a portion of the evening where guests are encouraged to show off their moves on the dance floor.

Whether the songs are played by an in-house DJ or thanks to an iTunes playlist, most wedding venues pay a fee to a copyright collective, like the Society of Composers, Authors and Music Publishers of Canada (SOCAN), for the right to blast copyrighted music during events, says Hood.

However, non-traditional venues, like farms, might not make those payments. Then, a court would have to determine whether the wedding reception was a private or public event, says Sartorio. A court would likely consider the size and make up of the guest list when making its decision.

It's a judgment call, says Hood, and the answer isn't clear. But if it's a group of close friends and family dancing to music played over speakers from an iPod, he says, "chances are the artists on your playlist won't come knocking."

Family reunions

Another situation that blurs the line between private and public is a family reunion.

It's not as cut and dried that all events held in public places are public and all those hosted in private residences are private, says Sartorio. Prior legal cases have shown that isn't always the case.

For a reunion held at a public park with speakers blasting pre-recorded music, "chances are you'll be OK," says Hood — so long as the guest list truly is family and not open to the public.

Street performances

Sometimes buskers play original music, but often it's covers of other artists' works pedestrians hear when passing by them.

SOCAN offers tariff licences for buskers and strolling musicians to prevent them from copyright infringement when they perform in public. Musicians can expect to pay $32.55 daily for a three-month maximum cost of $222.93.

Other public performances that necessitate a SOCAN tariff licence include comedy and magic shows, fireworks displays and parades with marching bands or floats with music.