What Cheer, Netop?

My grandfather told me this story from when he was living in Port Washington.

He was in a glee club there, and for one concert they had prepared a song which began with a piano accompaniament, then had a long a capella section, and then had another section with piano.

The night of the performance, they began singing the piece and during the a capella section they noticed the conductor was looking more and more nervous as they got closer and closer to the point at which the piano would join in. Finally, they reached that point, the pianist started playing, and the conductor looked very relieved and blew him a kiss.

It had turned out that during the a capella section the singers had gradually gone flat, but that the pianist had detected this and on starting up again played his part transposed a half-tone, bringing him into tune with what the singers were singing at that point.

( More about my grandfather, including a lot of possibly disturbing stuff )