Times have not been easy for SoundCloud. The 7-year-old music streaming service – with 175 million unique listeners every month – has become a kind of behemoth in the audio content creating and sharing space. Its growth, however, hasn't been free from controversy — mostly surrounding the violation of copyright laws protecting creators and publishers from possible infringement.

The U.K.'s Performing Rights Society for Music (PRS for Music) – which is responsible for collecting publishing royalties for musicians, radio plays, public performances and more – has continuously expressed dissatisfaction with the way the service handles (or doesn't handle) artist licensing.

"We have asked SoundCloud numerous times to recognize their responsibilities to take a license to stop the infringement of our members' copyrights but so far our requests have no been met," the company said in a press release on Thursday.

In a letter of claim to SoundCloud, PRS for Music provided a list of 4,500 musical works created by its members on the service that either needed to be licensed or removed from the site. In response, SoundCloud only took down 250 posts without any further statement.

Now, the organization has announced that it's taking legal action against SoundCloud and its inability to protect PRS for Music member artists.

This is a tough spot for the streaming service to be in — facing pressure from major labels like Sony to combat infringement while also getting heat from small-scale artists for compromising on the free sharing and collaborative ethos on which the service was built.

Although PRS for Music hasn't provided details about the nature of this "legal action," it "remain[s] hopeful that this matter can be resolved without the need for extended litigation."

At the end of the day, it's up to SoundCloud whether it wants to license these member artists or take them down from the site, but PRS for Music's ultimatum makes one thing very clear: it is imperative that appropriate action be taken immediately.

SoundCloud has yet to respond to this announcement.