Los Angeles: Soon after "What do you mean?" hitmaker Justin Bieber shared some songwriting advice with his fans, singer Charlie Puth stepped in to give some additional tips. Bieber had previously posted on Instagram a message to his fans about writing a song. "If you write music take notes from the greatest writer to ever do it Jason Boyd aka Poo bear," Bieber wrote to his followers. Shortly thereafter, Puth tweeted: "If you write music... Write from the heart. You don't take notes, you hear them." While he didn't mention Bieber's name, the "One call away" apparently shot down Bieber's message, reports aceshowbiz.com. It isn't the first time Puth has mocked Bieber. The 24-year-old singer yelled "F**k you Justin Bieber" while performing his Selena Gomez collaboration "We don't talk anymore" during a concert in Dallas back in March.