Climb up the wall and pull up on the ledge in front of the stained-glass window.

Carefully, hop on the rafters ahead (Walk+Jump) and carefully walk to the other side, avoiding the left hand part that collapses.

Jump the gap and drop down at the end.

Enter the small room with the organ and pick up the Diamond Ring. Exit the room and climb back on the rafters you came from.

Jump the gap and turn right to face the decrepit rafters. Take a look below to spot two Clips on a small ledge. Stand in front of the decrepit rafters and take a standing jump over them, holding Action in midair to grab the sill beyond. The rafters collapse whilst jumping over them and that way you can easily grab the sill.

Release and press Action again to grab the small ledge below. Pull up and pick up the M-V9 and Vector-R35 Clips. Hang from the ledge and drop to the ground.