'Drumming service' or 'drumhead service'?

Drumhead service in Edinburgh to mark the start of World War 1

Last week the North Belfast News carried an article by Liam Murphy on events in Belfast in 1966, the 50th anniversary of the 1916 Easter rebellion in Dublin.  In it he wrote:

Norman Porter, director of the Evangelical Protestant Society, suggested that the Orange Order engage in a drumming service or a rally in the King's Hall to coincide with the Casement Park event.  'The motto of the true Ulster Protestant is still: For God and Ulster.'

The term 'drumming service' caught my attention because there is no such thing as a 'drumming service'.  There is however a 'drumhead service' and that is something with which members of the Orange Order and those in military service would understand.

The following link will take you to a short video clip about drumhead services, especially in the context of the First World War.  http://bbc.in/116JseS