The Medford Council on Aging welcomes back the Tufts University student musical group Public Harmony for a free concert. Public Harmony’s musicians and singers combine their love of music and performing with community service. Each semester, the group performs at senior centers, nursing homes, children’s hospitals, and shelters in the Boston area, connecting communities through music. Coffee and desserts also will be provided. Sign-up begins at the Senior Center on Wednesday, September 11.