Each line he chanted alone, after the ancient Scottish custom, after which the congregation joined with him in the tune.

The custom survived from the time when psalm-books were in the hands of but few and the "lining" of the psalm was therefore necessary.
There was no haste to be done with the psalm.

Why should there be?
They had only one Sabbath in the week, and the whole day was before them.
The people surrendered themselves to the lead of Straight Rory with unmistakable delight in that part of "the exercises" of the day in which they were permitted to audibly join.

But of all the congregation, none enjoyed the singing more than the dear old women who sat in the front seats near the pulpit, their quiet old faces looking so sweet and pure under their snow-white "mutches." There they sat and sang and quavered, swaying their bodies with the tune in an ecstasy of restful joy.
Maimie had often heard St.Paul's before, but never as it was chanted by Straight Rory and sung by the Indian Lands congregation that day.
The extraordinary slides and slurs almost obliterated the notes of the original tune, and the "little kick," as Maimie called it, at the end of the second line, gave her a little start.
"Auntie," she whispered, "isn't it awfully queer ?" "Isn't it beautiful ?" her aunt answered, with an uncertain smile.

She was remembering how these winding, sliding, slurring old tunes had affected her when first she heard them in her husband's church years ago.