Not necessarily. In Canada, a musical work will fall into the public domain starting on January 1st of the year following a fifty year period after the death of the last surviving author. For instance, if the last surviving author died on say, July 15, 1940, the work will enter the public domain on January 1, 1991.
So, the process is a matter of finding out when the author(s) died. Of course, if the author is still alive then the work is protected by copyright and needs to be licensed.
Likewise, note that there are many copyrighted arrangements of public domain works that also need to be licensed when reproduced. If a song is in the public domain, and you’re reproducing your own arrangement, you do not require a licence and you don’t need to pay royalties.