Music by Kevin MacLeod (original composer: unknown). Available under the Creative Commons Attribution 3.0 Unported license. Download link: https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100862

MacLeod's description:

First Call
Genre: Unclassifiable
Length: 0:11
Instruments: Trumpets

AKA "Warning Call". Three trumpeter version of the 1804 military bugle call. I couldn't get the ensemble to do triple tonguing on the arpeggios. Oh well. Still does the job. Get ready!
ISRC: US-UAN-11-00862
Bright 2011