Artists need muses. Degas had ballet dancers; Erykah Badu, not unlike Aziz Ansari, has the phone. After her popular take on Drake’s “Hotline Bling,” Badu still has more to say about the devices people check obsessively and make calls from sparingly. “Phone Down,” which will be featured on her upcoming But You Caint Use My Phone mixtape, tackles the phenomenon of putting one’s phone down, or the inability to do so. In these here fast-moving digital times, is there anything more romantic than presence in the moment? Though it doesn’t have to be romantic. If you listen enough — as Badu sings “I can make you put your phone down” on repeat — it sounds more like a self-help mantra. Put Your Phone Down and Join the Cult of Badu.