Contributed by Kenneth Greiner / St. Augustine’s Tower, Hackney’s oldest building, is a late-medieval stone structure once connected to a long demolished church. At times used as a mortuary and tool shed, it’s now a museum, open once a month in this recently gentrified corner of East London. Inside the Tower are four floors for immersive art, connected by an agonizingly narrow set of stairs. Earlier this month, this improbable venue presented the group exhibition “Sonorous,” which concerned vibration as a means of communication. And it worked. The weathered crypts and headstones at the base of the tower echoed a somber song that the sound of the Tower bell magnified, rustling the cobwebs that rested in its eaves.