By Jaeden Pinder Dexter in the Newsagent got her stage name from a joke at a party in high school. “Someone was like, ‘What’s her name?’ And I said Dexter, because I thought that was so funny,” she recalls. (“In the Newsagent” took a bit more brainstorming, and came from the need to optimize her visibility in a sea of Google searches for a certain Showtime series.) Born Charmaine Ayoku, this south London singer-songwriter has been making music for half a decade, but had a major breakthrough with her debut mixtape, Time Flies, last fall. It’s a bedroom-pop record in sound and execution; she recorded most of it at her family home, and its style draws on early PinkPantheress and Clairo (one of Dexter’s favorites) along with Imogen Heap and SZA. Dexter’s sound is mesmerizing, but her lyrics are precise and confessional. She wants her music to feel warm and familiar, but “also [like you] had never heard it before.” “Special,” a twinkling low-key dance-pop track, is a shining example of what she does best.…