The 27-year-old Glee star's first album, Louder, became available to stream on iTunes on Tuesday.
Michele and Monteith starred together on Glee since the show's inception in 2009, and became a real-life couple in 2011. The two were still dating when the actor died in July 2013. Monteith, 31, died from a lethal combination of heroin and alcohol, although coroners reported that his death appeared accidental.
Michele co-wrote "If You Say So" in the days following Monteith's death, and the song is rumored to be based on the last words he said to her. The song narrates an exchange where Monteith tells Michele he loves her, she professes to love him more, and Monteith responds, "If you say so." Michele goes on to ask in the song, "How could you leave me this way?" and laments that, "I thought we would grow old."
Michele recently told V Magazine that, "I just feel like people should hear ["If You Say So"] and I don't know if I'm ever going to talk about it. It's just one of those things where I understand what it means and you can take it or leave it. That song is for me."
Louder will be available to download on March 3rd.