What will be the country's largest musical instrument is going up at Auckland's Holy Trinity Cathedral.

Holy Trinity has paid $4 million for a pipe organ, which is being transported here in seven 40 foot crates.

The first of the crates is being unloaded by a team of Englishmen, who're here specially to build the instrument - said to be the largest Cathedral organ built in Britain since 1928.

At 32 feet long at it's tallest point, the organ took an entire year to build, and will take another year to put up - so church-goers will need to get used to the roof-high silver scaffolding as part of their service.

Cathedral Organist Philip Smith said it's a very exciting day for the Cathedral, and for him.

"Six years in the planning, two years in the building, all very, very exciting. Lots of sleepless nights, because you only get to do this sort of thing once in a lifetime, so we really want to make sure we get it right."