Another Riddle

I can't find any other riddle from the same book that hardly uses any Redwall Map thinking like something that sounds burnt but alive between the pond and the orchard and all. So, here's one that hardly uses map thinking. Though it uses a lot of Redwall history......

'Twas I slew the Scourge in days of old,
Then I was one, but now we are two.
We who are dumb, yet sound so bold,
Days and night to order you.
We are those who announce a feast,
Or victories of the brave-hearted.
We are those whose solemn farewell,
Mark sadly a loved one departed.
On our oak see knowledge unfold,
We never speak 'til we're told?
We never speak 'til we're told.

Big Hint: It's something instrumental.