Complex sentence: In May 2016, Monstercat signed American producer Marshmello's single, Alone, which has amassed over 120 million views on YouTube, making it the most viewed video on their YouTube channel.
Split into simpler sentences: In May 2016, Monstercat signed American producer Marshmello's single, Alone. Its music video has amassed over 120 million views on YouTube, making it the most viewed video on their YouTube channel.