Numbers 10:3

And when they shall blow with them, all the assembly shall assemble themselves to thee at the door of the tabernacle of the congregation.

When they shall blow. There seem to have been signals made by a difference in the loudness and variety in the notes, suited for different occasions, and which experience made the Israelites easily distinguish. A simple uniform sound by both trumpets summoned a general assembly of the people; the blast of a single trumpet convoked the princes to consult on public affairs; notes of some other kind were made to sound an alarm, whether for journeying or for war.