How do I know whether a song is protected by copyright?

In general, you must assume that music is protected by copyright. The only requirement is that a musical work has been created. Such a creation exists if the level of creation required by copyright law is reached. In the case of musical works, however, the requirements regarding the creative originality are not high. As such, a relatively low degree of creation is sufficient.

Each musical work is protected right from its creation – that it all that needs to be done in this regard.  A work does not become free in terms of copyright until the term of protection has expired. 

Good to know: You can determine the creators of a work by using the GEMA Search repertoire function if their works are part of the GEMA repertoire.