There are hits, and then there are songs that define periods of time—summers, years, eras, careers. And though they’ve enjoyed varying degrees of success as performers, The-Dream and Sean Garrett have made their mark on culture most by writing an almost frightening number of songs for other artists—songs you’ve lived with. Garrett—who earned the nickname “The Pen”—will forever be associated with the R&B-infused crunk of Usher’s 2004 smash “Yeah!” and Ciara’s 2004 debut “Goodies,” but he’s also put in shifts for Beyoncé, Mario, Ludacris, Kelis, Brandy, Britney Spears, and Nicki Minaj, for whom he helped write 2010’s “Massive Attack,” another debut single. In the other corner, The-Dream’s songwriting credits read like a list of monuments: Rihanna’s “Umbrella,” Beyoncé’s “Single Ladies,” Kanye’s “All of the Lights,” and Watch the Throne’s brooding, Frank Ocean-enriched opener “No Church in the Wild.” Their hits may have been hard to escape, but their discographies go deeper than that; be sure and get the full brunt of their catalogs by way of the official Sean “The Pen” Garrett and The-Dream Cheat Sheet playlist, curated by Apple Music host Lowkey.