“Soul” is less a style of music than it is a quality. As surely as “head music” refers to cerebral stuff whose complexity is its selling point, soul music is a sound that speaks to you on an intangible level that runs even deeper than the heart. That can refer to an overt religious element (like the gospel-charged music that Ray Charles pioneered) but doesn’t have to: It just has to be transmitted from and to one’s basic human essence. That’s why Akua Allrich, known and celebrated in D.C. (and beyond) for her jazz vocal stylings, nonetheless has a status as a “soul singer” that even the staunchest genre purists can’t question. Allrich is a disciple of Nina Simone, with a similarly eclectic approach to repertoire and performance style, but with a generous addition of touches from her own West African heritage (Miriam Makeba is another huge influence). It makes for a unique artistic vision that’s reflected on her new album, titled—what else?—Soul Singer. Akua Allrich performs at 6 p.m. at the Kennedy Center Millennium Stage, 2700 F St. NW. Free. (202) 467-4600. kennedy-center.org.