“I found a deeper well” is the thesis statement of Kacey Musgraves’s new album, the source of its title, and the refrain of its first single. That deeper well, the richer self-knowledge that Musgraves says is the source of this music, has come via familiar conduits: meditation, mantras, mushrooms, and Manhattan, where the album was mostly written and recorded. Now, as she recently explained to the Cut, she is “way more grounded” and making serious, reflective music to prove it—a fairly dramatic shift from the pop experiments of Star-crossed.The song “Deeper Well” outlines this story neatly, a strategic release befitting Musgraves’s status as singer-songwriter turned singer-songwriter-A-lister: it is gently folk-poppy in an on-trend way that nods to the outsized success of her recent collaborators Noah…