For when the trumpet shall be blown;
Then, when the horn is blown.
When the Horn is blown
For when the trumpet is sounded
So if the horn/bugle/trumpet was blown in
The Day that the horn is blown
So when the Trumpet will be blown
And when the trumpet is sounded
Then when the Trumpet will be blown (a second time)
And the day the trumpet (of the Prophet's call to the people) is sounded
Then, when the Trumpet is sounded (i.e. its second blowing)