A high-wire exam at Old South Church

These rich photographs were shot earlier today by the Globe's David Ryan at Old South Church in Boston's Copley Square, where an aerial engineer named Emma Francis was examining the crack in the wall caused by MBTA excavation work beside the landmark church early last month.

I just got off the phone with the Rev. Nancy S. Taylor, the senior minister of the United Church of Christ congregation, who told me the "roped access" was necessary to determine whether there is any risk of plaster falling from the cracked wall when the organ is played. It turns out that the church's organ, with something like 6,500 pipes, causes the building to shake when it is played, and it hasn't been used since the damage because of a fear that plaster could fall onto the organ's pipes or electronics (apparently there is no risk to people because they don't stand under that wall). Today's tests found the plaster to be quite loose, but it remains to be decided whether the loose parts can simply be removed, or can be temporarily repaired, or whether the organ will be unusable for months or years.

Taylor said the roped access was achieved by removing a part of a window that is about 70 feet up, and putting two ropes through to anchor the engineer, and then hoisting her up on a harness with all kinds of equipment used to assess the damage.

The church is quite eager to resume the use of its organ for worship, weddings, and concerts.

"We're in a specialty business here -- we don't sell a product, our purpose is to worship, and a part of the way we do that is with beautiful music,'' Taylor said. "This organ represents to us a particular and unique and precious instrumental treasure that also manages to fill that space, so the thought of being without it for what could be months or years is hard to imagine.''

Taylor said the church has been making do with a variety of instruments -- in addition to its Steinway piano, it has used cello, trumpet, clarinet, drums, mandolin and flute.

Meanwhile the repairs to the church appear to be quite a ways off. Taylor said there is still an ongoing forensic investigation to determine what happened, but that it appears that an MBTA contractor somehow hit the church's pilings (the church, like everything else in the area, is built on fill, so it's held up by pilings) with a high-pressure jet of grout slurry, and the impact on the pilings lifted the church's wall.

"There's really no agreed understanding as to what happened, so the forensic investigation will involve test pits and mathematical computations where they plug in all kinds of things and look at the crack and try to say why it went the way it did,'' Taylor said. "But the MBTA is still taking responsibility and assuring us that the church should bear no cost at all in this.''