The bulk of Be Still is a selection of hymns and songs Dave Douglas’ late mother requested for her memorial service in 2011. Aoife O’Donovan (Crooked Still) sings on six numbers, marking the first time in nearly 20 years of recording diverse bands and projects that Douglas has incorporated a vocalist. “Be Still My Soul” opens the album with O’Donovan, Douglas, and tenor saxophonist Jon Irabagon each performing individually and distinctly accompanied by the wholly supportive rhythm section of pianist Matt Mitchell, bassist Linda Oh, and drummer Rudy Royston. All three front line instruments harmonize on the introduction to the bluegrass song “High on a Mountain,” while “God Be with You” and its emotive harmonies reach a spiritually soulful high. Four originals by the inventive bandleader tend to be on the explorative side but still mirror the spirit of reflection of the traditional selections.