There are few summertime activities more satisfying than catching some live music at a park while sipping a cool, refreshing beverage. And that’s the kind of atmosphere you can expect at Yerba Buena Gardens Festival, a summer concert series in the outdoor area of the venerable SoMA arts institution. For the May 7 edition, Oakland bands Elephantine and The Seshen are slated to perform. Elephantine is the new project of musician, entrepreneur, and activist Zakiya Harris, who creates rich neo-soul steeped in Afro-futurist philosophy. While Harris is also a solo artist, she recently joined forces with fellow powerhouse vocalists Tossie Long and Solas B. Lalgee and several other musicians, and together, they make big, ecstatic tracks with life-affirming messages. The Seshen, a multifaceted seven-piece band with a similarly soulful vibe that incorporates electronic elements and jazzy instrumentation, will also dazzle audiences with virtuosic musicianship.