As the founder, director and guiding spirit of Oakland-based CO-LLAB Choir Cava Menzies has created a powerful new vehicle for bringing musicians together for synergistic collaboration. The 24-member contemporary vocal ensemble develops new works by vocalists and singer-songwriters through a rigorous process of co-arranging and co-writing material. The ensemble also collaborates with professional artists on studio recordings and performances, and for the group’s YBG Festival debut they’re presenting a soul-steeped program with special guests such as soul star Martin Luther McCoy and piano virtuoso Kev Choice. The show highlights the original compositions created by the singer-songwriters and arrangers within the ensemble, including a new composition commissioned by Yerba Buena Gardens Festival. “Our purpose as an ensemble is to express healing, love and unity through sound,” says Menzies, an esteemed pianist, vocalist, songwriter and educator who helped found Oakland School for the Arts.