As music-streaming services blossomed over the past decade, so have mobile apps and sites allowing users to create MP3 files from songs streamed on free services such as Alphabet Inc.’s YouTube. Fans can listen to the songs without YouTube’s ads—and without having to buy the songs or pay for a subscription service such as Spotify AB and Apple Inc.’s Apple Music.
Source: Music Industry’s Latest Piracy Threat: Stream Ripping – WSJ