This book sort of reads a wee bit like a TV series (home-front setting), with the reader discovering a little bit more about each character each week. It is a comfortable read, despite all the drama.
The trials and tribulations of the choir members become inconsequential when they get together and sing for Britain. Singing for Britain might seem like an exaggeration, however in times of war when the country is fighting to survive it probably feels as if they are.
There are a lot of different character story-lines connected via the occasional sing-song. The choir becomes the busy traffic junction for all the members. It is something consistent during a time of fear, worry and turbulence.
I think the author should have emphasized the choir more and the moments of pure harmony between the singers. Those few minutes of joy and happiness struggle to stay afloat in the sheer volume of sub-plots. It was a little disjointed, perhaps because it needed more focus on one boat in a sea of ships.